Aircraft fuselage micro-rib surface paving method and drag reduction performance calculation method thereof

Abstract

The application discloses an aircraft fuselage micro-rib surface paving mode and a drag reduction performance calculation method thereof, and belongs to the technical field of aeronautical engineering. The application realizes efficient formulation of the aircraft fuselage micro-rib surface paving mode by only associating the micro-rib surface paving division with the fuselage surface and only selecting the small-rib parameters of the single-piece micro-rib surface in association with the fuselage surface flow field, and appropriately considering the influence of the fuselage surface flow field on the position and size of the single-piece micro-rib surface division. Meanwhile, in combination with the characteristics of continuous change of the fuselage surface flow field and the micro-rib surface drag reduction performance modeling calculation method, the small-rib parameters of the center point of the single-piece micro-rib surface are taken as the small-rib parameters of the whole micro-rib surface, the micro-rib surface area characteristics are calculated simply, and efficient evaluation of the drag reduction performance of different micro-rib surface paving modes is realized.

Description

Technical Field

[0001] This invention belongs to the field of aerospace engineering technology, and in particular relates to aircraft microrib drag reduction surface technology, specifically a method for laying microribs on the surface of an aircraft fuselage and a method for calculating its drag reduction performance. Background Technology

[0002] Frictional drag accounts for over 50% of the drag in civil aircraft, and this type of drag is independent of the specific aircraft layout, depending solely on the boundary layer state of the fuselage surface. Particularly for aircraft fuselages with long flow directions, due to the high local Reynolds number, most areas are controlled by turbulent boundary layers that generate significant frictional drag due to flow transitions. To meet the requirements of green aviation development, reducing the drag of civil aircraft, especially the frictional drag on the fuselage surface, has become a hot research topic in aircraft drag reduction technology.

[0003] With the development of aerospace materials and high-precision manufacturing technology for complex surfaces, microrib turbulence drag reduction technology, derived from the biomimetic structure of shark skin, has attracted increasing attention due to its advantages of low cost, high returns, simple maintenance, and wide applicability. Its basic principle involves attaching downstream microribs to the fuselage surface, with a height not exceeding a certain thickness at the bottom of the turbulent boundary layer. The typical cross-section of these ribs is trapezoidal or triangular, with a certain spacing between adjacent ribs. The protruding rib structure reduces flow structure abruptness by suppressing the spanwise oscillation of quasi-flowing vortices within the turbulent boundary layer, thereby suppressing turbulent dissipation and ultimately reducing turbulent drag.

[0004] Although current civil aircraft fuselages are relatively regular cylindrical in shape, the flow field at different locations on the fuselage surface varies due to factors such as the pilot's limited field of view causing the forward fuselage to tilt downwards, the rear fuselage tilting upwards to avoid ground contact, wing washing, and interference. In particular, the wall friction stress and local flow direction differ significantly. To achieve optimal drag reduction performance, the microribs applied to the fuselage must match the size and orientation of the microribs with the local flow field. Typically, the dimensionless spacing s+ of the microribs is around 15, and the angle between the microrib orientation and the local flow direction does not exceed 10°. When the dimensionless spacing s+ and the angle of the microribs do not match the local flow field, it may lead to reduced drag reduction effectiveness or even increased flight drag.

[0005] Due to limitations imposed by manufacturing, installation, use, and maintenance, in practical engineering applications, fuselage microribs are typically applied using a zoned application method. This involves preparing a certain number of microrib films of specific sizes and then neatly laying them out to completely cover the fuselage surface, with the ribs within each film having the same size and orientation. Therefore, a reasonable microrib application method needs to be developed to ensure, within engineering constraints, that the rib parameters on the microrib surface match the local flow field parameters as closely as possible. Simultaneously, to effectively evaluate the selected microrib application scheme, a drag reduction performance calculation method corresponding to the microrib application method needs to be established to guide the improvement and optimization of the microrib application scheme. Summary of the Invention

[0006] To address the challenge of rationally defining the surface layout of aircraft fuselage microribs within engineering constraints and efficiently determining the surface area of ​​each microrib, this invention proposes a surface layout method for aircraft fuselage microribs and a method for calculating its drag reduction performance. This method involves dividing the microrib surface layout into zones that are solely related to the fuselage surface curvature and selecting the rib parameters of individual microribs that are solely related to the fuselage surface flow field. It also appropriately considers the influence of the fuselage surface flow field on the position and size of the individual microrib surface zones, thereby achieving efficient formulation of the aircraft fuselage microrib surface layout method. On the other hand, taking into account the continuous change of the flow field on the fuselage surface and the modeling calculation method of the drag reduction performance of the microrib surface, a simplified processing method is proposed, which uses the small rib parameters at the center point of a single microrib surface as the small rib parameters of the entire microrib surface, so as to achieve efficient evaluation of the drag reduction performance of different microrib surface laying methods.

[0007] This invention discloses a method for applying microribs to the surface of an aircraft fuselage, comprising the following specific steps:

[0008] Step 1: Based on the geometric characteristics of the aircraft fuselage, take the nose vertex as the origin O. b Define the body coordinate system O b (x b y b z b );x b The axis is along the straight section of the fuselage; z b The axis is within the plane of symmetry of the fuselage.

[0009] Step 2: Divide the aircraft fuselage into multiple sub-regions based on the continuity of the aircraft fuselage surface, ensuring that the surface in each sub-region is smooth and continuous.

[0010] Step 3: Determine the surface area of ​​the individual microribs in each sub-region.

[0011] 301, along x b m axes perpendicular to x b The plane of the axis, denoted as S_i. i Its intersection with the curved surface of the fuselage sub-region forms the fuselage cross-sectional curve C. i .

[0012] 302. Curve C of the i-th fuselage section i Arrange n on top i Let P be a point j. ij , through P ij Draw a straight line L perpendicular to the curved surface of the fuselage. ijz , and the fuselage cross-section curve C i Tangent line L ijy .

[0013] 303. Using point P ij O is the origin ij Establish local coordinate system O ij (x ij y ij z ij ); with L ijz For z ij Axis, with L ijy For y ij axis.

[0014] 304. Regarding P ij Point, along the local coordinate system x ij Draw a straight line L along the axis ijx And project it along the direction of the fuselage curve normal to form the fuselage surface curve C. ijx .

[0015] 305. If P ij The location is along the x-axis of the body coordinate system. b If the surface boundary of the microrib has been determined at the adjacent station in front of or behind the axis, then the boundary of the microrib is perpendicular to x. b Planar intercept curve C of the axis ijx Curve C is intercepted through the plane containing the front and rear boundaries of the micro-rib surface. ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2.

[0016] If P ij The location is along the x-axis of the body coordinate system. b If the surface boundary of the microrib is not defined at adjacent stations on the axis, then draw the adjacent fuselage section curves and curve C. ijx The intersection point Qij And in curve C ijx P is determined above ij With Q ij Midpoint M ij Through point M ij Curve C is intercepted in the plane ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2.

[0017] 306. For two endpoints N ij 1 and N ij 2. Construct x-axis perpendicular to the body coordinate system. b The plane of the axis intersects with the curved surface of the fuselage, forming the fuselage section curve D. ij 1 and D ij 2.

[0018] 307. Following the methods in sub-steps 303 and 304, complete the process related to P. ij Adjacent points P with the same station i(j-1) and P i(j+1) The corresponding fuselage surface curve C i(j-1)x 'and C i(j+1)x ', and its corresponding line segment endpoint N i(j-1) 1. N i(j-1) 2 and N i(j+1) 1. N i(j+1) 2;308, on fuselage section curve D ij 1. Determine N ij 1 and N i(j-1) The midpoint of 1 is S. ij 1. Determine N ij 1 and N i(j+1) The midpoint of 1 is T. ij 1; In the fuselage section curve D ij 2. Determine N ij 2 and N i(j-1) The midpoint of 2 is S. ij 2. Determine N ij 2 and N i(j+1) The midpoint of 2 is T. ij 2; Let S be the number of points. ij 1. T ij 1 cut D ij The curve segment formed by 1 is E ij ; Record S ij 2. T ij 2 cuts D ij The curve segment formed by 2 is F ij Connection point Sij 1. S ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as U. ij Connection point T ij 1. T ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as V. ij E ij F ij U ij V ij The enclosed area is defined by P. ij The surface area of ​​a single micro-rib centered on a point.

[0019] Step 4: Denote the reference point L for the direction of the small ribs on the surface of the micro-rib as ijx For P ij Point the small rib, and move it towards P ij Projection of the fuselage curve tangent plane at point P; further, take point P. ij Starting from point O, and relative to the local coordinate system O b (x b y b z b ) of x b A unit vector P whose positive angle with the axis is acute and which is parallel to the projection of the small rib. ijg Let P be the unit vector. ijg The angle between the x-axis and the small rib direction angle is the magnitude of the angle, when the unit vector P ijg When the angle between the direction and the positive y-axis is acute, the direction angle takes a positive value; otherwise, it takes a negative value, denoted as the small rib direction angle α.

[0020] Step 5: Sequentially complete the calculation of all specific points P on the fuselage cross-sectional curve determined by the m planes. ij The surface boundary of the corresponding single micro rib is used to determine the micro rib surface paving area of ​​the entire fuselage surface.

[0021] Based on the above microrib surface mounting method, the specific steps for calculating its drag reduction performance are as follows:

[0022] Step A: Based on the microrib surface partitioning determined in the above steps, complete the computational mesh generation, ensuring that each individual microrib surface is an independent boundary. For the flight state to be evaluated, obtain the basic flow field through numerical simulation based on the RANS method.

[0023] Step B: For the center point P of each individual micro-rib surface ij Extract the wall shear stress τ, the dimensionless wall height y+ = 1 to 100 at the extraction point, the flow field density ρ, dynamic viscosity coefficient μ, and velocity components vx, vy, vz.

[0024] Step C: For point P ijOn the surface of a single microrib at a given location, let the spacing between the ribs be s and the direction of the ribs be α; determine point P according to the formula. ij The dimensionless width parameter s+=s(τρ) of the microrib surface at that location. 0.5 / μ, and here s+ is approximated as s+ in the entire surface area of ​​the monolithic microrib.

[0025] Step D: Move point P ij The velocity component at point P ij Local coordinate system O b (x b y b z b ) of x b axis and y b Axis projection determines velocity component V xij and V yij If V xij If it is less than 0, then V will be simultaneously... xij and V yij Reverse the sign and determine point P using trigonometric function formulas. ij The flow angle at point β is β = arctan(V) yij / V xij When V xij When approaching 0, β = 90° - arccot(V) yij / V xij If the β obtained according to the formula exceeds 90°, it is corrected by subtracting 180° from the calculated value to ensure that the value of β is within ±90°; further, point P is obtained. ij The deviation of the direction of the small rib from the flow direction is γ = abs(β-α). When γ exceeds 90°, it is corrected by subtracting the calculated value from 180° to ensure that the value of γ is in the range of 0° to 90°. Here, γ is approximated as γ in the entire surface area of ​​the single micro rib.

[0026] Step E: Sequentially complete the extraction and calculation of the dimensionless parameter s+ and the angle γ of the deviation between the rib and the local flow direction for the surface area of ​​the single micro-rib corresponding to all specific points on the fuselage cross-section curve determined by m planes.

[0027] Step F: Combining the microrib surface modeling calculation method based on the RANS equation k-ω model, determine the turbulent dissipation rate ω′=f(ω0,y) at the computational grid on the body surface after the microrib surface is laid. + 0,s + ,γ), where ω0 is the local turbulent dissipation rate calculated from the baseline state without microribs, and y +0 represents the dimensionless height of the first local grid layer. The turbulent dissipation rate at all computational grids of the fuselage surface with microribs is modified to the new turbulent dissipation rate ω′, and the flow field is calculated again to finally obtain the drag reduction performance after subdividing multiple regions and applying microribs to the surface.

[0028] The advantages of this invention are:

[0029] 1. The surface area of ​​the single micro rib proposed in this invention is only related to the curved shape of the aircraft fuselage. The division method is simple and easy to implement. Except for the edge of the fuselage curved surface, the boundary of the area is approximately rectangular, and the size range is suitable for single-person operation, which is beneficial for micro rib surface cutting and installation.

[0030] 2. This invention ignores the impact of discontinuous rib shapes at the boundaries of different microrib surface regions on aerodynamic performance. From the perspective of the continuity of the flow field on the aircraft fuselage surface, the dimensionless size and direction parameters of the ribs at the center point of the region are approximated as the rib parameters of the entire single region. Within the allowable range of calculation accuracy, the calculation of rib parameters of the fuselage region on the surface of the microrib is simplified, which significantly improves the calculation efficiency of the drag reduction performance of the microrib surface.

[0031] 3. This invention provides a method for calculating the dimensionless parameter s+ that characterizes the rib features of a microrib within a single microrib surface region, and the method for calculating the rib direction and the angle γ between the rib and the local flow direction. Combined with the independent mesh boundary representing the fuselage surface of a single region, the method can quickly modify the rib modeling parameter ω' within the entire single region by finding the calculation boundary number. This allows for the efficient determination of drag reduction performance when different rib spacing and rib direction parameters are selected on the single microrib surface, as well as the overall drag reduction performance of the aircraft fuselage when microrib surface regions with different rib parameters are combined. This is beneficial for evaluating and optimizing the rib parameter selection strategy for different regions of the aircraft fuselage microrib surface. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the surface application method of the microribs on the aircraft fuselage according to the present invention.

[0033] Figure 2 This is a flowchart of the method for calculating the drag reduction performance of microribs on the aircraft fuselage according to the present invention;

[0034] Figure 3 For the aircraft body coordinate system O b (x b y b z b ) Schematic diagram;

[0035] Figure 4 A schematic diagram illustrating the division of multiple sub-regions in the aircraft fuselage;

[0036] Figure 5The fuselage cross-sectional curve formed by the intersection with the fuselage sub-region curved surface, and the points P arranged on the curve. ij Location diagram;

[0037] Figure 6 For point P ij Establish local coordinate system O ij (x ij y ij z ij ) Schematic diagram;

[0038] Figure 7 It is at point P ij Draw the fuselage surface curve C ijx Then, determine point Q. ij and M ij Schematic diagram;

[0039] Figure 8 It is at point P ij A schematic diagram illustrating the method of drawing points around the perimeter;

[0040] Figure 9 With P ij A schematic diagram of the surface boundary curve of a single micro-rib centered on a point;

[0041] Figure 10 With P ij A schematic diagram of the rib direction α on the surface of a single microrib centered at a point;

[0042] Figure 11 With P ij A schematic diagram of extracting flow field information and obtaining the rib spacing s on the surface of a single microrib centered at a point;

[0043] Figure 12 With P ij A schematic diagram of the flow angle β on the surface of a single microrib centered at a point;

[0044] Figure 13 With P ij A schematic diagram of the deviation angle γ between the surface ribs of a single microrib centered on a point and the local flow direction.

[0045] Figure 14 It is at the edge of the curved surface of the fuselage with P ij A schematic diagram of the surface of a single microrib centered on a point.

[0046] Figure 15 Simulation diagram of γ values ​​in various areas of the fuselage surface after the installation of small ribs;

[0047] Figure 16 The dimensionless dimension s of the ribs in each area of ​​the fuselage surface after the small ribs are installed. + Simulation diagram;

[0048] Figure 17 Simulation diagram of the theoretical drag reduction rate of each area on the fuselage surface after the installation of small ribs;

[0049] Figure 18 This is a simulation diagram showing the difference in wall shear stress in each region after drag reduction using the method of this invention and after theoretical drag reduction. Detailed Implementation

[0050] The present invention relates to a method for surface mounting of microribs on aircraft fuselages, such as... Figure 1 As shown, the specific steps are as follows:

[0051] Step 1: Based on the geometric characteristics of the aircraft fuselage, take the nose vertex as the origin O. b Define the body coordinate system.

[0052] Define the body coordinate system as O b (x b y b z b ); where x b The axis is the direction of the straight section of the fuselage, with positive pointing from the nose to the tail; z b The axis is within the fuselage's plane of symmetry, perpendicular to x. b The axis of the shaft is positive when the direction from the root chord of the vertical shaft to the tip chord is positive; according to x b z b The axis is determined by the right-hand rule. b Axial direction, such as Figure 3 As shown.

[0053] Step 2: Based on the surface continuity of the aircraft fuselage, divide the fuselage into multiple sub-regions, ensuring that the surfaces within each sub-region are smooth and continuous; for example... Figure 4 The aircraft fuselage shown can be divided into three sub-regions based on surface continuity: the basic fuselage surface, the cockpit surface, and the fairing bulge surface. The following steps then determine the surface area of ​​a single microrib for each sub-region.

[0054] Step 3: Determine the surface area of ​​the individual microribs in each sub-region.

[0055] 301, along x b m axes perpendicular to x b The plane of the axis, the value of m can be determined according to the actual situation, constrained by the boundary length of the surface region of the single micro-rib. Let the i-th plane be S. i Its intersection with the curved surface of the fuselage sub-region forms the fuselage cross-sectional curve C. i ,like Figure 5 As shown.

[0056] 302. Curve C of the i-th fuselage section i Arrange n on top in points i The value of can be determined according to the actual situation, and is also constrained by the boundary length of the surface region of a single microrib. Let the j-th point be P. ij , through P ij Draw a straight line L perpendicular to the curved surface of the fuselage. ijz , and the fuselage cross-section curve C i Tangent line L ijy .

[0057] 303. Establish the local coordinate system O ij (x ij y ij z ij ); with point P ij O is the origin ij , with L ijz For z ij The axis, pointing outwards from the fuselage curve, is positive, with L as the axis. ijy For y ij axis, take along x b P observed in the positive axis direction ij The counterclockwise direction of the point is y ij The positive direction of the axis is determined by the right-hand rule. ij Axis, such as Figure 6 As shown.

[0058] 304. Regarding P ij Point, along the local coordinate system x ij Draw a straight line L on the axis ijx And project it along the direction of the fuselage curve normal to form the fuselage surface curve C. ijx ,like Figure 7 As shown.

[0059] 305. If P ij Location (C) i Along the body coordinate system x b Adjacent station in front of or behind the axis (C) i-1 Or C i+1 Given that the surface boundary of the microrib has been determined, then the boundary perpendicular to x is taken as the boundary of the microrib surface. b Planar intercept curve C of the axis ijx Curve C is intercepted through the plane containing the front and rear boundaries of the micro-rib surface. ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2.

[0060] If P ij Location (C) i Along the body coordinate system xb If the surface boundary of the microrib is not defined at adjacent stations on the axis, then the cross-sectional curve of the adjacent fuselage (C) is plotted. i-1 Or C i+1 ) and curve C ijx The intersection point Q ij And in curve C ijx P is determined above ij With Q ij Midpoint M ij Through point M ij Curve C is intercepted in the plane ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2, such as Figure 8 As shown.

[0061] 306. Regarding the over-P ij Point curve segment C ijx The two endpoints N ij 1 and N ij 2. Construct x-axis perpendicular to the body coordinate system. b The plane of the axis intersects with the curved surface of the fuselage, forming the fuselage section curve D. ij 1 and D ij 2.

[0062] 307. Following the methods in sub-steps 303 and 304, complete the process related to P. ij Adjacent points P at the same station location (located on the same fuselage cross-section curve) i(j-1) and P i(j+1) The corresponding fuselage surface curve C i(j-1)x 'and C i(j+1)x '; and its corresponding line segment endpoint N i(j-1) 1. N i(j-1) 2 and N i(j+1) 1. N i(j+1) 2.

[0063] 308. For example Figure 9 As shown, in the fuselage section curve D ij 1. Determine N ij 1 and N i(j-1) The midpoint of 1 is S. ij 1. Determine N ij 1 and N i(j+1) The midpoint of 1 is T. ij 1. In the fuselage section curve D ij 2. Determine N ij 2 and N i(j-1) The midpoint of 2 is S. ij 2. Determine Nij 2 and N i(j+1) The midpoint of 2 is T. ij 2. Let S be the number of digits. ij 1. T ij 1 cut D ij The curve segment formed by 1 is E ij ; Record S ij 2. T ij 2 cuts D ij The curve segment formed by 2 is F ij Connection point S ij 1. S ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as U. ij Connection point T ij 1. T ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as V. ij .

[0064] 309. When P ij The point is located within the curved surface of the fuselage, and the complete curve segment E can be obtained simultaneously. ij F ij U ij V ij At that time, from the curved line segment E ij F ij U ij V ij The enclosed area is defined by P. ij E is a single micro-rib surface area centered on a point. ij F ij U ij V ij This refers to the boundary of the surface area of ​​the single microrib. Otherwise, the plane S needs to be readjusted as a whole. i and point P ij The distribution of the curve segment E is to ensure its stability. ij F ij U ij V ij It is a complete surface area that can be enclosed as a single microrib.

[0065] like Figure 14 As shown, when P ij When the point is near the edge of the curved surface of the fuselage (for irregular edges, i.e., not straight lines), it is impossible to adjust S... i and point P ij If the distribution is obtained completely and can be closed into a single micro-rib surface region, then the first step is to estimate the partitions to determine the approximate single micro-rib surface region; further, based on the approximate partitions, n i Adjust each point to ensure P ijThe point is located at the center of the surface area of ​​the micro-rib to be determined, and then curve segments are generated except for the edges of the fuselage curved surface. Finally, based on the generated curve segments (E) ij F ij U ij V ij (Several of them) and curved edges form a closed edge as the surface boundary of a single microrib.

[0066] Step 4: Sequentially complete the calculation of all specific points P on the fuselage cross-sectional curve determined by the m planes. ij The corresponding surface boundary of a single microrib is determined, thereby defining the microrib surface coverage area of ​​the entire fuselage, totaling n1 + n2 + ... + nm. Step 4: As... Figure 10 As shown, for P ij Let L be the reference point for the direction of the small ribs on the surface of a single microrib centered at point 1. ijx For P ij Point the small rib, and move it towards P ij The projection of the fuselage curve tangent plane at point P. Further, take point P. ij Starting from point O, and relative to the local coordinate system O b (x b y b z b ) of x b A unit vector P whose positive angle with the axis is acute and which is parallel to the projection of the small rib. ijg Let P be the unit vector. ijg The angle between the x-axis and the small rib direction angle is the magnitude of the angle, when the unit vector P ijg When the angle with the positive y-axis is acute, the direction angle is positive; otherwise, it is negative, denoted as the rib direction angle α. To ensure the rationality of the surface paving of a single microrib, the internal ribs of a single microrib must be in the same direction and have the same size, and the length of its boundary curve segment must be in the range of 300mm to 1300mm.

[0067] This allows us to confirm the size of each area on the fuselage surface and the parameters of the microribs, which can then be used to complete the installation of the microribs on the surface.

[0068] For the above-mentioned micro-ribbed paving method, its drag reduction performance was calculated, such as... Figure 2 As shown, the specific method is as follows:

[0069] Step A: Based on the microrib surface partitioning determined in the above steps, complete the computational mesh generation, ensuring that each individual microrib surface is an independent boundary. For the flight state to be evaluated, obtain the basic flow field through numerical simulation based on the RANS method.

[0070] Step B: For the center point P of each individual micro-rib surface ijExtract the wall shear stress τ, the dimensionless wall height y+ at the extraction point (within a value w between 1 and 100), the flow field density ρ, dynamic viscosity coefficient μ, and velocity components vx, vy, vz, as shown below. Figure 11 As shown.

[0071] Step C: For point P ij Let s be the spacing between the ribs on the surface of a single microrib at a given location, and α be the direction of the ribs. Determine point P using the formula. ij The dimensionless width parameter s+=s(τρ) of the microrib surface at that location. 0.5 / μ, and here s+ is approximated as s+ in the entire surface area of ​​the monolithic microrib.

[0072] Step D: As Figure 12 As shown, point P ij The velocity component at point P ij Local coordinate system O b (x b y b z b ) of x b axis and y b Axis projection determines velocity component V xij and V yij If V xij If it is less than 0, then V will be simultaneously... xij and V yij Reverse the sign and determine point P using trigonometric function formulas. ij The flow angle at point β is β = arctan(V) yij / V xij When V xij When approaching 0, β = 90° - arccot(V) yij / V xij If β obtained from the formula exceeds 90°, it is corrected by subtracting 180° from the calculated value to ensure that the value of β is within ±90°. Figure 13 As shown, point P is further obtained. ij The deviation of the direction of the small rib from the flow direction is γ = abs(β-α). When γ exceeds 90°, it is corrected by subtracting the calculated value from 180° to ensure that the value of γ is in the range of 0° to 90°. Here, γ is approximated as γ in the entire surface area of ​​the single micro rib.

[0073] Step E: Sequentially complete the extraction and calculation of the dimensionless parameter s+ and the angle γ of the deviation between the rib and the local flow direction for the surface area of ​​the single micro-rib corresponding to all specific points on the fuselage cross-section curve determined by m planes.

[0074] Step F: Combining the microrib surface modeling calculation method based on the RANS equation k-ω model, determine the turbulent dissipation rate ω′=f(ω0,y) at the computational grid on the body surface after the microrib surface is laid. + 0,s + ,γ), where ω0 is the local turbulent dissipation rate calculated from the baseline state without microribs, and y + 0 represents the dimensionless height of the first local grid layer. The turbulent dissipation rates at all computational grid points on the fuselage surface where the microribs are applied are modified to the new turbulent dissipation rate ω′, and the flow field calculation is performed again. Finally, the drag reduction performance after applying microribs to multiple subdivided regions can be obtained.

[0075] This invention applies the microrib surface application method of the aircraft fuselage to a clean fuselage model simplified from the NASA Common Transport Aircraft (CRM) model, and performs drag reduction performance calculations. The calculations were performed on the industrial general-purpose solver platform ANSYS Fluent. The governing equations were discretized using the finite volume method to create three-dimensional, compressible Reynolds-averaged Navier-Stokes equations, employing a pressure-based steady-state solver. The pressure-velocity coupling was determined using the COUPLED algorithm, gradient reconstruction used the node-based Green-Gauss method, and the convection term discretization used a second-order upwind scheme. The incoming flow Ma was 0.785, the angle of attack α was 3°, the incoming static pressure was 66579.3 Pa, and the static temperature was 278.7 K. The fuselage surface was divided into 10 × 10 zones (flow direction × circumferential direction), and the drag reduction effect of this configuration with 30 μm microribs (s) covering the entire fuselage was examined. Figure 15 As shown, the γ values ​​read from each region are displayed; for example... Figure 16 As shown, the dimensionless dimensions s of the microribs in each region are illustrated. + ;like Figure 17 As shown, the theoretical drag reduction rate for each region is illustrated; for example... Figure 18 As shown, the difference in wall shear stress in each region after modular drag reduction according to the present invention and after theoretical drag reduction is illustrated. It can be seen that the difference in drag reduction effect between the modular and theoretical methods is small. Under this operating condition, the estimated theoretical drag reduction rate of the total fuselage friction is 6.628%, and the modular drag reduction rate is 6.782%, with a difference of 2.3%, meeting the engineering accuracy requirements.

[0076] This invention discloses a method for applying microribs to the surface of an aircraft fuselage and calculating their drag reduction performance. It is simple and easy to implement, ignoring the aerodynamic performance impact caused by the discontinuity in the shape of the microribs at the boundaries of different individual microrib surface regions. Within the allowable range of calculation accuracy, it simplifies the calculation of microrib parameters for the fuselage region where the microribs are applied, significantly improving the calculation efficiency of the drag reduction performance of the microrib surface. By combining the independent mesh boundaries characterizing individual fuselage regions, the microrib modeling parameter ω′ within the entire individual region can be quickly modified by looking up the calculation boundary number. This allows for the efficient determination of the drag reduction performance when different microrib spacing and orientation parameters are selected for individual microrib surfaces, as well as the overall drag reduction performance of the aircraft fuselage when combining microrib surface regions with different microrib parameters. This facilitates the evaluation and optimization of microrib parameter selection strategies for different regions of the aircraft fuselage microrib surface.

Claims

1. A method for applying microribs to the surface of an aircraft fuselage, characterized in that: The specific steps are as follows: Step 1: Based on the geometric characteristics of the aircraft fuselage, take the nose vertex as the origin O. b Define the body coordinate system O b (x b y b z b );x b The axis is along the straight section of the fuselage; z b The axis is within the plane of symmetry of the fuselage; Step 2: Divide the aircraft fuselage into multiple sub-regions based on the continuity of the aircraft fuselage surface, ensuring that the surface within each sub-region is smooth and continuous; Step 3: Determine the surface area of ​​the individual microribs in each sub-region; a. Along x b m axes perpendicular to x b The plane of the axis, denoted as S_i. i Its intersection with the curved surface of the fuselage sub-region forms the fuselage cross-sectional curve C. i ; b. Curve C of the i-th fuselage section i Arrange n on top i Let P be a point j. ij , through P ij Draw a straight line L perpendicular to the curved surface of the fuselage. ijz , and the fuselage cross-section curve C i Tangent line L ijy ; c. Using point P ij O is the origin ij Establish local coordinate system O ij (x ij y ij z ij ); with L ijz For z ij Axis, with L ijy For y ij axis; d. Regarding P ij Point, along the local coordinate system x ij Draw a straight line L on the axis ijx And project it along the direction of the fuselage curve normal to form the fuselage surface curve C. ijx ; e. If P ij The location is along the x-axis of the body coordinate system. b If the surface boundary of the microrib has been determined at the adjacent station in front of or behind the axis, then the boundary of the microrib is perpendicular to x. b Planar intercept curve C of the axis ijx Curve C is intercepted through the plane containing the front and rear boundaries of the micro-rib surface. ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2; If P ij The location is along the x-axis of the body coordinate system. b If the surface boundary of the microrib is not defined at adjacent stations on the axis, then draw the adjacent fuselage section curves and curve C. ijx The intersection point Q ij And in curve C ijx P is determined above ij With Q ij Midpoint M ij Through point M ij Curve C is intercepted in the plane ijx Forming curve segment C ijx ', along the body coordinate system x b Let N be the endpoint of the line segment closest to the origin of the body coordinate system. ij 1, with the other endpoint being N. ij 2; f. For the two endpoints N ij 1 and N ij 2. Construct x-axis perpendicular to the body coordinate system. b The plane of the axis intersects with the curved surface of the fuselage, forming the fuselage section curve D. ij 1 and D ij 2; g. Following sub-steps c and d, complete the process related to P. ij Adjacent points P with the same station i(j-1) and P i(j+1) The corresponding fuselage surface curve C i(j-1)x 'and C i(j+1)x '; and its corresponding line segment endpoint N i(j-1) 1. N i(j-1) 2 and N i(j+1) 1. N i(j+1) 2; h, in the fuselage section curve D ij 1. Determine N ij 1 and N i(j-1) The midpoint of 1 is S. ij 1. Determine N ij 1 and N i(j+1) The midpoint of 1 is T. ij 1; In the fuselage section curve D ij 2. Determine N ij 2 and N i(j-1) The midpoint of 2 is S. ij 2. Determine N ij 2 and N i(j+1) The midpoint of 2 is T. ij 2; Let S be the number of points. ij 1. T ij 1 cut D ij The curve segment formed by 1 is E ij ; Record S ij 2. T ij 2 cuts D ij The curve segment formed by 2 is F ij Connection point S ij 1. S ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as U. ij Connection point T ij 1. T ij 2. Draw a curved line segment on the fuselage surface along the normal direction of the fuselage surface, denoted as V. ij E ij F ij U ij V ij The enclosed area is defined by P. ij The surface area of ​​a single micro-ribbed strip centered on a point; Step 4: Denote the reference point L for the direction of the small ribs on the surface of the micro-rib as ijx For P ij Point the small rib, and move it towards P ij Projection of the fuselage curve tangent plane at point P; further, take point P. ij Starting from point O, and relative to the local coordinate system O b (x b y b z b ) of x b A unit vector P whose positive angle with the axis is acute and which is parallel to the projection of the small rib. ijg Let P be the unit vector. ijg The angle between the x-axis and the small rib direction angle is the magnitude of the angle, when the unit vector P ijg When the angle between the direction and the positive y-axis is acute, the direction angle takes a positive value; otherwise, it takes a negative value, denoted as the small rib direction angle α. Step 5: Sequentially complete the calculation of all specific points P on the fuselage cross-sectional curve determined by the m planes. ij The surface boundary of the corresponding single micro rib is used to determine the micro rib surface paving area of ​​the entire fuselage surface.

2. The surface mounting method for microribs on an aircraft fuselage as described in claim 1, characterized in that: When P ij The point is located within the curved surface of the fuselage, and the complete curve segment E can be obtained simultaneously. ij F ij U ij V ij At that time, by the curved line segment, E ij F ij U ij V ij This is the boundary of the surface area of ​​the single micro-rib; otherwise, the plane S is readjusted as a whole. i and point P ij The distribution of the curve segment E is to ensure its stability. ij F ij U ij V ij The complete and enclosed surface area of ​​the microrib; When P ij When a point is near the edge of the fuselage curved surface, the first step is to pre-estimate the approximate surface area of ​​a single micro-rib by dividing the area into zones; then, based on the approximate zones, the n... i Adjust each point to ensure P ij The point is located at the center of the surface region of the micro-rib to be determined, and then curve segments are generated except for the edges of the fuselage surface. Finally, based on the generated E... ij F ij U ij V ij Several of the fuselage curved surfaces are enclosed by a closed edge line, which serves as the surface boundary of a single micro-rib.

3. The method for applying microribs to the surface of an aircraft fuselage as described in claim 1, characterized in that: The internal ribs on the surface of a single micro-rib are aligned in the same direction and have the same size.

4. The surface mounting method for microribs on an aircraft fuselage as described in claim 1, characterized in that: The length of the surface boundary curve segment of a single microrib ranges from 300mm to 1300mm.

5. The method for calculating the drag reduction performance of the microrib surface laying method for aircraft fuselage as described in claim 1, characterized in that: The specific steps are as follows: Step A: Based on the microrib surface partitioning determined in the above steps, complete the computational mesh generation, ensuring that each individual microrib surface is an independent boundary. For the flight state to be evaluated, obtain the basic flow field through numerical simulation based on the RANS method. Step B: For the center point P of each individual micro-rib surface ij Extract the wall shear stress τ, the dimensionless wall height y+ = 1 to 100 at the extraction point, the flow field density ρ, dynamic viscosity coefficient μ, and velocity components vx, vy, vz; Step C: For point P ij On the surface of a single microrib at a given location, let the spacing between the ribs be s and the direction of the ribs be α; determine point P according to the formula. ij The dimensionless width parameter s+=s(τρ) of the microrib surface at that location. 0.5 / μ, and here s+ is approximated as s+ in the entire surface area of ​​the monolithic microrib; Step D: Move point P ij The velocity component at point P ij Local coordinate system O b (x b y b z b ) of x b axis and y b Axis projection determines velocity component V xij and V yij If V xij If it is less than 0, then V will be simultaneously... xij and V yij Reverse the sign and determine point P using trigonometric function formulas. ij The flow angle at point β is β = arctan(V) yij / V xij When V xij When approaching 0, β = 90° - arccot(V) yij / V xij If β obtained according to the formula exceeds 90°, then the calculated value is corrected by subtracting 180° to ensure that the value of β is within ±90°; further, point P is obtained. ij The deviation of the direction of the small rib from the flow direction is γ = abs(β-α). When γ exceeds 90°, it is corrected by subtracting the calculated value from 180° to ensure that the value of γ is in the range of 0° to 90°. Here, γ is approximated as γ in the entire surface area of ​​the single micro rib. Step E: Sequentially complete the extraction and calculation of the dimensionless parameter s+ and the deviation angle γ between the rib and the local flow direction for the surface area of ​​the single micro rib corresponding to all specific points on the fuselage cross-section curve determined by m planes; Step F: Combining the microrib surface modeling calculation method based on the RANS equation k-ω model, determine the turbulent dissipation rate ω′=f(ω0,y) at the computational grid on the body surface after the microrib surface is laid. + 0,s + ,γ), where ω0 is the local turbulent dissipation rate calculated from the baseline state without microribs, and y + 0 represents the dimensionless height of the first grid layer in the local area; The turbulent dissipation rate of all computational grids on the fuselage surface with microribs was modified to a new turbulent dissipation rate ω′, and the flow field was calculated again to finally obtain the drag reduction performance after subdividing multiple regions and laying microribs on the surface.

6. The method for calculating the drag reduction performance of the microrib surface laying method for aircraft fuselage as described in claim 5, characterized in that: By combining the independent mesh boundaries of the fuselage surface representing a single region, the modification of the small rib modeling parameter ω′ in the entire single region can be quickly completed by looking up the calculation boundary number. This allows us to obtain the drag reduction performance of a single microrib surface with different parameters such as small rib spacing and small rib direction, as well as the overall drag reduction performance of the aircraft fuselage when combining microrib surface regions with different small rib parameters.

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