Estimation method of longitudinal coefficients of ground effect vehicles and its aerodynamic characteristics analysis system

Abstract

The present application relates to a kind of ground effect wing ship longitudinal coefficient estimation method and its aerodynamic characteristic analysis system, belong to the technical field of ground effect wing ship. It covers preliminary design ground effect wing ship scheme, design and manufacture wind tunnel model, obtain data by 3 times variable flight height test, and utilize these data to deduce the mathematical expression of ground effect wing ship longitudinal aerodynamic coefficient, estimate the longitudinal aerodynamic characteristic in any flight height state by the mathematical expression of ground effect wing ship longitudinal aerodynamic coefficient, to simplify test procedure, reduce test number. The present application significantly reduces the workload of model blowing test by combining theoretical analysis with a small amount of test data, shortens the research and development cycle, reduces the consumption of funds. At the same time, the method can accurately obtain the key partial derivative and relative ground effect height in the stability calculation of ground effect wing ship, improve the design efficiency and accuracy, and has important promoting effect on the development and application of ground effect wing ship technology.

Description

Technical Field

[0001] This invention relates to the field of ground effect vehicle technology, and in particular to a method for estimating the longitudinal coefficient of a ground effect vehicle and its aerodynamic characteristic analysis system. Background Technology

[0002] With the development of technology in the field of ground effect vehicles, key technologies for stable flight close to the water surface have emerged. This technology has the characteristics of providing efficient lift and good stability when flying close to the water surface at low altitudes, which leads to the development of methods for obtaining aerodynamic data through wind tunnel tests to analyze flight quality and corresponding test equipment.

[0003] In related technologies, designers first design a preliminary scheme based on the design task book or technical specifications, then design and fabricate a model, and conduct wind tunnel tests on the model. Based on the aerodynamic characteristic data obtained from the wind tunnel tests, various calculations are performed to verify whether the design meets the requirements. However, if several or most of the requirements are not met, the design scheme must be modified, the model must be fabricated again, and a second round of wind tunnel tests must be conducted. This process is usually repeated multiple times to obtain a scheme that meets the design requirements for use in the next stage of detailed design.

[0004] Therefore, the aforementioned wind tunnel testing method and related design process often require multiple iterations of design, model fabrication, and wind tunnel testing to obtain a solution that meets the design requirements, resulting in long processing time and high costs. Summary of the Invention

[0005] To address the shortcomings of existing production technologies, the applicant provides a method for estimating the longitudinal coefficient of a ground effect vehicle and its aerodynamic characteristic analysis system. This method obtains necessary aerodynamic characteristic data based on a small amount of wind tunnel model blowing data through theoretical estimation, thereby shortening the design cycle, reducing testing costs, lowering development costs, and improving design efficiency.

[0006] The technical solution adopted in this invention is as follows: A method for estimating the longitudinal coefficient of a ground effect vehicle, comprising the following steps:

[0007] Step 1: Preliminary design. Based on the design task book or technical specifications of the ground effect vehicle, determine the scale ratio of the wind tunnel model of the preliminary scheme and design the wind tunnel model.

[0008] Step 2, Wind Tunnel Model Manufacturing and Installation: Based on the scaled-down model, manufacture the wind tunnel model and install an adjustable-height simulated ground effect surface floor. The floor is adjusted relative to the model via a screw mechanism and tie rods to simulate changes in flight altitude.

[0009] Step 3: Conduct 3 variable flight altitude tests, including 1 test in the no-ground effect state and 2 tests in the ground effect state. Measure the lift coefficient data in the no-ground effect state and measure the lift coefficient and pitch moment coefficient data at different flight altitudes in the ground effect state.

[0010] Step four: Establish mathematical expressions for aerodynamic coefficients. Based on the experimental data in step three, derive mathematical expressions for lift coefficient and pitching moment coefficient; where lift coefficient and pitching moment coefficient have a linear relationship with the logarithm of relative flight altitude.

[0011] Step 5: Using the derived mathematical expression, calculate the estimated longitudinal aerodynamic characteristics of the ground effect vehicle at any flight altitude.

[0012] As a further improvement to the above technical solution:

[0013] Preferably, the variable flight altitude test in step three includes:

[0014] In the absence of ground effect, the floor is adjusted to a position far away from the model to ensure that the wind tunnel test data is not affected by the ground effect of the floor, and the lift coefficient data is measured at this time.

[0015] Preferably, the variable flight altitude test in step three further includes:

[0016] Lift coefficient and pitch moment coefficient data were measured at different flight altitudes under two different ground effect conditions.

[0017] Preferably, the wind tunnel model includes a floor, which is connected to the upper wall of the wind tunnel model via at least one tie rod, and a lead screw mechanism is provided at the connection point; a ground effect vehicle model is provided below the floor, and the lower part of the ground effect vehicle model is connected to a fairing provided on the lower wall of the wind tunnel model.

[0018] More preferably, the front of the ground effect vehicle model is connected to the front fairing disposed on the lower wall of the wind tunnel model via a joint, and the tail of the ground effect vehicle model extends a tail link, the end of which is connected to the rear fairing disposed on the lower wall of the wind tunnel.

[0019] Preferably, the lead screw mechanism and tie rod are used to realize the vertical movement of the floor to simulate the change in the flight altitude of the ground effect vehicle; the front fairing and the rear fairing are used to realize the rotation of the ground effect vehicle model around the joint to simulate the change in the pitch angle of the ground effect vehicle.

[0020] Preferably, the wind tunnel model simulates different flight attitudes by adjusting the pitch angle.

[0021] A ground effect vehicle aerodynamic characteristic analysis system is provided, which uses the above-mentioned ground effect vehicle longitudinal coefficient estimation method to estimate the longitudinal aerodynamic coefficient of the ground effect vehicle and outputs the stability calculation results.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention overcomes the shortcomings of traditional methods, which require multiple iterations of design, model fabrication, and wind tests to obtain a solution that meets design requirements, resulting in long time consumption and high costs. This invention requires only three variable flight altitude tests (including one test in no-ground effect state and two tests in ground effect state) to obtain an estimated value of the longitudinal aerodynamic characteristics of a ground effect vehicle at any flight altitude. This significantly reduces the workload of model wind tests, shortens the design cycle, and lowers development costs. The technical solution of this invention can be widely applied to the estimation of longitudinal coefficients for ground effect vehicles with different aerodynamic layouts. By adjusting the test parameters and coefficients in the mathematical expression, this technical solution can adapt to the design requirements of different ground effect vehicles, demonstrating broad applicability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the wind tunnel testing device of the present invention.

[0025] Figure 2 For the present invention A schematic diagram of the curve.

[0026] Figure 3 For the present invention A schematic diagram of the curve.

[0027] Figure 4 For the present invention A schematic diagram of the curve.

[0028] Figure 5 For the present invention A schematic diagram of the curve.

[0029] Figure 6 This diagram illustrates the determination of ground effect height and C value according to the present invention.

[0030] Figure 7 This is a diagram showing the determination of the M value in this invention.

[0031] Figure 8 This is a schematic diagram of the method for estimating the longitudinal coefficient of a ground effect vehicle according to the present invention.

[0032] Figure 9 This is a calculation diagram of the wind tunnel test in the ground effect state and the wind tunnel test at ground effect altitudes H1 and H2 according to the present invention.

[0033] The components include: 1. Screw mechanism; 2. Tie rod; 3. Ground effect vehicle model; 4. Front fairing; 5. Joint; 6. Tail connecting rod; 7. Rear fairing; 8. Floor. Detailed Implementation

[0034] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0036] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0037] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0038] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0039] like Figures 1-9 As shown, the present invention provides a method for estimating the longitudinal coefficient of a ground effect vehicle, specifically including the following steps:

[0040] In this embodiment, the preliminary design involves: first, developing a rough design framework based on the design task book or technical specifications, and analyzing the feasibility of implementing the framework, including the feasibility of using selectable power systems, structural materials, construction processes, and testing methods; then, completing a preliminary scheme design, and determining the scale of the preliminary scheme's wind tunnel model based on the wind tunnel laboratory's testing facilities, instruments, and model connection methods, and designing the wind tunnel model. The purpose of wind tunnel model testing is to measure the aerodynamic characteristics of the design scheme model under different flight conditions, and to determine the aerodynamic efficiency of corresponding aerodynamic components by changing their installation angles. The test results provide the necessary parameters for stability calculations and a basis for further modifications to the scheme. Simultaneously, they provide technical data for verifying the effectiveness of the design method and making necessary corrections.

[0041] In this embodiment, the wind tunnel model is designed, manufactured, and installed as follows: Model fabrication and the fabrication of connecting struts to the wind tunnel balance are completed according to the design drawings of the scaled-down wind tunnel model, and a wind tunnel test outline is prepared. The wind tunnel model is installed in the wind tunnel laboratory, along with an adjustable-height floor simulating the ground effect surface. This floor can be adjusted relative to the wind tunnel model to simulate changes in ground effect height. The parameters that determine the steady longitudinal aerodynamic characteristics (aerodynamic forces or aerodynamic moments) of the ground effect wing vehicle include... , and (here For speed, The relative flight altitude of a ground effect vehicle when its center of gravity leaves the surface. The mean aerodynamic chord of the ground effect wing. =Height of center of gravity from the floor - Distance from center of gravity to the model baseline To fly high, (Pitch angle). Wind tunnel tests are conducted according to the wind tunnel test outline. Due to the relative altitude of the aerodynamic forces (or aerodynamic torques), rate of change with The decrease and increase of [something] is the effect of the ground effect. Therefore, when [something] decreases and increases, [something] increases. When the size is small, the test points in the test plan should be more densely packed, generally for: =0.05, 0.075, 0.10, 0.15, 0.20, 0.30, 0.50, 0.80, ∞, ( (Indicates no floor), pitch angle for: =-4°, -2°, 0°, 2°, 4°, 6°, 8°. The test plan will be implemented according to the test points of the above test scheme.

[0042] Specifically, the wind tunnel test apparatus includes a floor 8, which is connected to the upper wall of the wind tunnel model via a tie rod 2, and a lead screw mechanism 1 is provided at the connection point. A ground effect vehicle (GEV) model 3 is positioned below the floor 8, and its lower part is connected to a fairing mounted on the lower wall of the wind tunnel model. The front of the GEV model 3 is connected to a front fairing 4 mounted on the lower wall of the wind tunnel model via a connector 5. A tail link 6 extends from the tail of the GEV model 3, and the end of the tail link 6 is connected to a rear fairing 7 mounted on the lower wall. The front and rear fairings 4 and 7 are used to allow the GEV model to rotate around the connector, simulating changes in the pitch angle of the GEV. The wind tunnel model can simulate the pitch angle of the GEV by adjusting its pitch angle. The changes; the tail link 6 is used for guiding the rear support rod and the fairing 7.

[0043] In this embodiment, the aerodynamic characteristics of the ground effect vehicle include: The drag coefficient, The lift coefficient, This is the lateral force coefficient. This is the tilt moment coefficient. This is the yaw moment coefficient. is the pitch moment coefficient, where For wing area, For the exhibition length, For speed head, Let be the air density. The aerodynamic characteristics of a ground effect vehicle (GEV) flying far from the surface are essentially the same as those of an aircraft. However, when a GEV flies in the ground effect zone, its aerodynamic characteristics exhibit a strong nonlinear relationship with flight altitude, such as... Figure 2 The aerodynamic lift coefficient shown As relative altitude The changes clearly demonstrate this nonlinear characteristic. Here Figure 2 merely (a fixed pitch angle) A test curve (below) when the pitch angle is... When changing, Not only does its shape change, but it also moves up and down, because it is sensitive to different... , They are different. Figure 2 middle Defined as relative ground effect height, For the corresponding (Lift coefficient). Relative flight altitude of the local effect vehicle. Less than At that time, the presence of the ground surface affects the aerodynamic characteristics of the ground effect vehicle; while at relative flight altitude... Greater than At that time, the presence of the ground surface no longer affects the aerodynamic characteristics of the ground effect vehicle. Therefore, when At this time, it can be assumed that the ground effect vehicle flies within the ground effect zone. At this time, it can be considered that the ground effect vehicle flies outside the ground effect zone, just like an airplane, and is not affected by the ground effect. From Figure 2 It can also be seen that the closer the ground effect vehicle is to the ground surface, the more pronounced the change in lift coefficient. And the closer it gets to... The smaller the change, the greater the change. If we express this using the rate of change of the lift coefficient with respect to relative altitude, then... , .here for When kept constant, the corresponding lift coefficient with respect to relative flight altitude The partial derivatives, i.e., in The slope of the curve at a given point; this value is negative. Similarly... for When kept constant, the corresponding lift coefficient with respect to relative flight altitude The partial derivatives, i.e., in The slope of the curve at a given point is also negative. Since a larger negative value indicates a steeper slope and more drastic change, and represents a smaller value, therefore, there is... , In short, Figure 2 This indicates that while the partial derivative of the lift coefficient with respect to flight altitude is not constant within the ground effect region, its variation is monotonic. These fundamental characteristics of the lift coefficient of ground effect vehicles also represent the fundamental characteristics of the aerodynamic coefficients of other ground effect vehicles, namely, they all change with relative flight altitude. The changes are non-linear and monotonic. However, their difference lies in the defined relative ground effect height. They are not the same, for example, using Defined It is different from using Defined The aerodynamic coefficient of a ground effect vehicle varies with relative flight altitude. In addition to exhibiting nonlinear variation, it also varies with pitch angle within a certain range. It changes linearly, such as Figure 3As shown. In summary, maintain the pitch angle. The aerodynamic coefficient remains constant with relative flight altitude. The changes are non-linear; maintaining relative altitude The aerodynamic coefficient remains constant and varies with the pitch angle within a certain range. The change is linear, which is the basic characteristic of the aerodynamic properties of ground effect vehicles.

[0044] In this embodiment, the lift coefficient and pitching moment coefficient relative flight altitude The variation pattern: Numerous wind tunnel tests show that the lift coefficient As relative altitude The variation pattern is non-linear and exhibits a relatively consistent monotonic trend. However, through the collation and analysis of a large amount of wind tunnel model blowing data, it was found that if... Figure 2 of x-coordinate of the curve Change to ,but It becomes essentially linear. Because within a certain range, the pitching moment coefficient... With lift coefficient There is a linear relationship between them. Therefore, If it is a straight line, then It should also be a straight line, and a large amount of wind tunnel test data has confirmed this pattern of change. It was also found that if relative flight altitude is used... natural logarithm The x-axis also conforms to this "linear" pattern. For example... Figure 3 The data shown is based on experimental data from a certain ground effect vehicle model, and this data is based on relative flight altitude. =0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 0.97, pitch angle Measured at 0°, 2°, and 4°, and with... Plot it as the x-axis. Figure 3 This indicates that, considering the inherent errors in the experimental data, it is entirely reasonable to assume that... When it remains unchanged, Follow The change is indeed a straight line, because almost all the test points are on a straight line.

[0045] In this embodiment, the aerodynamic coefficient , The mathematical expression is derived as follows:

[0046] Expression: Due to certain Within the range of values, fixed , It is a straight line (e.g.) Figure 4 );fixed ,but It is also a straight line (such as) Figure 3 Then we have: (express When kept constant, the aerodynamic lift coefficient with respect to pitch angle The partial derivatives are The function, and (Irrelevant) (express When kept constant, the aerodynamic lift coefficient is related to The partial derivatives are The function, and (Irrelevant). Through mathematical derivation, a simplified mathematical expression for the lift coefficient can be obtained:

[0047] (Formula 1)

[0048] In the formula, It is the relative ground effect height, and its limiting condition is: (when (After-effect no longer exists), and There are also limitations. It is necessary to make It lies within a linear segment. It is a state without ground effect ( The slope of the lift line, It is related to the aerodynamic layout. As can be seen from Equation 1, when... ,Right now hour, This is the formula for the aircraft's lift coefficient, also known as the lift coefficient in the absence of ground effect. And from... Figure 4 In As can be seen from the lines, The slope of the straight segment of the line should be in a state of no ground effect ( The slope of the lift line, that is ,from Figure 4 This can be obtained from [the source]. At the same time... Line and The pitch angle corresponding to the intersection of the axes is called the pitch angle at zero lift. The pitch angle at zero lift This will be used to obtain the subsequent zero lift moment coefficient. Formula 1 for the lift coefficient of a ground effect vehicle The cross term coefficient, It is closely related to the aerodynamic layout, and at the same time, in Equation 1 and Is with and Irrelevant constants;

[0049] expression: and Very similar, such as Figure 5 For different Downwind tunnel test data Curve. Through mathematical derivation, a simplified mathematical expression for the torque coefficient is obtained:

[0050] (Formula 2)

[0051] In the formula, It is a state without ground effect ( The zero lift moment coefficient is closely related to the aerodynamic layout. It is a state without ground effect ( Torque coefficient curve The slope of is the static stability in the ground-effect-free state. From Equation 2, it can be seen that when... hour, This is the formula for the longitudinal moment of a typical aircraft. It can be done Figure 5 of As previously known, this can be obtained by using a curve. Figure 4 In The line can be obtained Line and The pitch angle corresponding to the intersection of the axes is called the pitch angle at zero lift. Use this pitch angle The corresponding position can be In the curve Get the corresponding information online Value, that is .

[0052] because and Very similar, that is to say, to a certain extent Within the range of values, fixed , It's a straight line. Thus, from... Figure 5 In A right triangle can be drawn online, and the slope of this right triangle represents the static stability in the ground-effect-free state. Similar to Equation 1 of the formula for the lift coefficient of a ground effect vehicle, Equation 2 of the formula for the moment coefficient of a ground effect vehicle... The cross term coefficient, It is also closely related to the aerodynamic layout.

[0053] In this embodiment, Expressions and The method for determining the intersection term in the expression is as follows:

[0054] like Figure 6 As shown, relative ground effect height Method for determining:

[0055] The relative ground effect height can be determined using data from three high-altitude wind tunnel tests. The experiment included one no-ground-effect test and two ground-effect test. The wind tunnel model was tested at a fixed pitch angle. Three tests were conducted, with the following flight altitudes being... , and Because I don't know But from Figure 2 It can be known that when Ground effect vehicles fly outside the ground effect zone, just like airplanes, without the influence of the ground effect, and their lift coefficient is low. This is a fixed value. Therefore, a ground effect-free state test is first conducted, during which the floor needs to be adjusted to a position far away from the model (i.e.,...). Much larger To ensure that wind tunnel test data is not affected by the ground effect of the floor, the data obtained in this way... It should be accurate. Then, conduct separate high-altitude flights. and The experiment yielded the corresponding results. and Finally, based on the experimental data, with As the x-axis, with Draw two intersecting straight lines on the ordinate, one of which is... and The extension of the line connecting the two points, and the other line is parallel to... The horizontal axis has the following values: The horizontal line, the x-coordinate value corresponding to the intersection of the two lines is the horizontal line. Therefore, we can obtain Due to different Different straight lines have different intersection points. But it has changed, and thus a series of subsequent changes can be obtained. Changes in relative ground effect height ;

[0056] Intersection terms in the expression Method for determining:

[0057] by For example, the corresponding relative ground effect height is From the simplified mathematical expression of the lift coefficient (Equation 1), the cross term is obtained. The expression:

[0058] (Formula 3)

[0059] In Formula 3, It is a state without ground effect ( The slope of the lift line, from Figure 4 of The slope of a straight line segment can be obtained, that is... Value. Due to (Equation 1) and Is with and Irrelevant constants, chosen here .so, , , and All have been determined, and only one remains in (Formula 3). . It can be done Figure 6 The transformation graph, on the horizontal axis Find the point Draw a parallel line through this point The vertical line of the ordinate, and the line from... and The point where the line connecting two points, or the extension of the line connecting them, intersects is the corresponding point. Value, that is Finally, substituting the obtained values ​​into equation (3), we get... value.

[0060] Intersection terms in the expression Method for determining:

[0061] Still with For example, the corresponding relative ground effect height is From the simplified mathematical expression of the torque coefficient (Equation 2), the cross term is obtained. The expression:

[0062] (Formula 4)

[0063] In Formula 4, It is a state without ground effect ( Zero lift torque coefficient, It is a state without ground effect ( Torque coefficient curve The slope of the slope represents the static stability of the ground-effect-free state. As explained earlier, through... Figure 4 of lines and Figure 5 of The line can be obtained Then through Figure 5 In The slope of the right triangle on the line gives the static stability in the ground-effect-free state. .

[0064] Similarly, due to Equation 2 , and All are with and Irrelevant constants, chosen here .so, , , , and All have been determined, and only one remains in (Formula 4). It needs to be determined.

[0065] because and Very similar, within a certain range If it is a straight line, then It should also be a straight line, such as... Figure 7 From Convert to Similarly, on the horizontal axis Find the point Draw a parallel line through this point The vertical line of the ordinate, and the line from... and The point where the line connecting two points, or the line extending from those two points intersects, is the corresponding point. Value, that is Finally, substituting the obtained values ​​into equation four, we get... value.

[0066] In this embodiment, the method for estimating the longitudinal coefficient of the ground effect vehicle is as follows:

[0067] First, based on the design task book or technical specifications (provided by the customer), conduct a preliminary design of the ground effect vehicle, complete a preliminary design scheme, determine the scale ratio of the wind tunnel model of the preliminary scheme, and design the wind tunnel model.

[0068] Second, complete the manufacturing and installation of the wind tunnel model, and simultaneously complete the installation of an adjustable-height floor simulating the ground effect surface. Conduct three variable-fly-rate tests: one in a non-ground effect state and two in a ground effect state; among which, in the non-ground effect state ( At a certain fixed pitch angle Below, measured Lift coefficient at time The data is a fixed value. Then the pitch angle is changed. , measured and Data, and plotting curves and Curve. Two ground effect states. and At a certain fixed pitch angle Below, measured , , and data;

[0069] Third, calculate the aerodynamic coefficient. The coefficients of the mathematical expression (Equation 1);

[0070] ①、 : by drawing Curve determination The slope of the straight segment of a line That is, the state without ground effect ( The slope of the lift line;

[0071] ②、 At a fixed pitch angle Below, measured High-altitude flight test data;

[0072] ③、 At a fixed pitch angle Below, the variable flight altitude test was measured. , and Use the data from three points to plot the x-axis. Convert to x-coordinate of A straight line, a straight line is and The extension of a line connecting two points will be parallel to the other line. The horizontal axis has the following values: When two horizontal lines intersect, the x-coordinate of the intersection point is _____. Therefore, we can obtain ; ④、 :exist The x-axis of the graph Find the point Draw a parallel line through this point The vertical line of the ordinate, and the line from... and The point where the line connecting two points, or the extension of the line connecting them, intersects is the corresponding point. Value, that is Value; ⑤ The above-obtained , , , and Substituting into equation (3), we get value;

[0073] Fifth, calculate the aerodynamic coefficient. The coefficients of the mathematical expression (Equation 2);

[0074] ①、 By determining curve and The pitch angle at the intersection of the axes when zero lift is obtained. ;

[0075] ②、 :exist of Determining the pitch angle on the curve corresponding Value, that is ;

[0076] ③、 :exist of Draw a right triangle on the line; the slope of this right triangle represents the static stability in the ground-effect-free state. ;

[0077] ④ At a fixed pitch angle Below, the variable flight altitude test was measured. and Plot the x-axis based on the data from two points. Convert to x-coordinate two points and And the line connecting the two points. On the x-axis Find the point Draw a parallel line through this point The vertical line of the ordinate, and the line from... and The point where the line connecting two points, or the line extending from those two points intersects, is the corresponding point. Value, that is value;

[0078] ⑤ The above-obtained , , , , and Substituting into equation (4), we get value.

[0079] In this embodiment, using The mathematical expression (Equation 1) and The mathematical expression (Equation 2) allows for the estimation of the longitudinal aerodynamic characteristics of the ground effect vehicle at any flight altitude by conducting only three variable flight altitude tests. This enables the determination of the aerodynamic lift and aerodynamic torque represented by these equations in various states. The value of the time can be obtained, which can greatly reduce the workload of model wind tests; it can also be obtained simply and accurately. and These two partial derivatives are crucial for the stability calculation of ground effect vehicles. However, obtaining them is laborious and prone to significant errors because it requires a large number of test points and precise plotting to determine the tangent at each point on the curve. In this embodiment, we utilize... or Due to the characteristics of a straight line, only one line needs to be drawn through... and The slope of the line corresponding to these two points is... or Using test data from three flight altitudes, the relative ground effect height for different aerodynamic configurations can be determined. .

[0080] In other embodiments, the present invention also provides a ground effect vehicle aerodynamic characteristic analysis system, which uses the above-mentioned ground effect vehicle longitudinal coefficient estimation method to estimate the longitudinal aerodynamic coefficient of the ground effect vehicle, thereby outputting stability calculation results.

[0081] In summary, in this embodiment, the present invention, through analysis of numerous wind tunnel test results, discovered a linear relationship between the longitudinal aerodynamic coefficient of the ground effect vehicle and the logarithm of its relative flight altitude, thereby creatively deriving... mathematical expressions and The advantages of this method include: firstly, the mathematical expression; secondly, the estimation value of the longitudinal aerodynamic characteristics of the ground effect vehicle at any flight altitude can be obtained by conducting only three variable flight altitude tests, which can greatly reduce the workload of model wind tests; and thirdly, the simple and accurate calculation of two partial derivatives that are very important in the stability calculation of the ground effect vehicle. and and the relative ground effect height of different aerodynamic configurations .

[0082] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for estimating the longitudinal coefficient of a ground effect vehicle, characterized in that, Includes the following steps: Step 1: Preliminary design. Based on the design task book or technical specifications of the ground effect vehicle, determine the scale ratio of the wind tunnel model of the preliminary scheme and design the wind tunnel model. Step 2, Wind Tunnel Model Manufacturing and Installation: Based on the scaled-down model, manufacture the wind tunnel model and install an adjustable-height simulated ground effect surface floor. The floor is adjusted relative to the model via a screw mechanism and tie rods to simulate changes in flight altitude. Step 3: Conduct 3 variable flight altitude tests, including 1 test in the no-ground effect state and 2 tests in the ground effect state. Measure the lift coefficient data in the no-ground effect state and measure the lift coefficient and pitch moment coefficient data at different flight altitudes in the ground effect state. The wind tunnel model was manufactured and installed, and the adjustable-height floor simulating the ground effect surface was installed. Three variable-altitude flight tests were conducted: one in a non-ground effect state and two in a ground effect state. At a certain fixed pitch angle Below, measured Lift coefficient at time The data is a fixed value; where, It is relative to the ground effect height; Change pitch angle again The lift coefficient was measured. and pitching moment coefficient , and Data, and plotting curves and curve; 2 ground effect states and At a certain fixed pitch angle Below, measured , , and data; Step four: Establish mathematical expressions for aerodynamic coefficients. Based on the experimental data in step three, derive mathematical expressions for lift coefficient and pitching moment coefficient; where lift coefficient and pitching moment coefficient have a linear relationship with the logarithm of relative flight altitude. The mathematical expression for the lift coefficient is: In the formula, It is relatively high. It is the relative ground effect height; its limiting condition is: Pitch angle It is necessary to make It lies within a linear segment; It is a state without ground effect. The slope of the lift line, Related to aerodynamic layout; The coefficient of the cross term; The mathematical expression for the pitch moment coefficient is: In the formula, State without ground effect The zero lift moment coefficient is closely related to the aerodynamic configuration. State without ground effect Torque coefficient curve The slope of the slope, i.e., the static stability of the ground-effect-free state; The coefficient of the cross term; Step 5: Using the derived mathematical expression, calculate the estimated longitudinal aerodynamic characteristics of the ground effect vehicle at any flight altitude.

2. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in claim 1, characterized in that, The variable flight altitude test in step three includes: In the absence of ground effect, the floor is adjusted to a position far away from the model to ensure that the wind tunnel test data is not affected by the ground effect of the floor, and the lift coefficient data is measured at this time.

3. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in claim 1, characterized in that, The variable flight altitude test in step three also includes: Lift coefficient and pitch moment coefficient data were measured at different flight altitudes under two different ground effect conditions.

4. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in any one of claims 1 to 3, characterized in that, The wind tunnel model includes a floor, which is connected to the upper wall of the wind tunnel model by at least one tie rod, and a lead screw mechanism is provided at the connection point; A ground effect vehicle model is installed below the floor, and the lower part of the ground effect vehicle model is connected to a fairing installed on the lower wall of the wind tunnel model.

5. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in claim 4, characterized in that, The front of the ground effect vehicle model is connected to the front fairing set on the lower wall of the wind tunnel model via a joint. The tail of the ground effect vehicle model extends into a tail link, and the end of the tail link is connected to the rear fairing set on the lower wall of the wind tunnel.

6. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in claim 4, characterized in that, The lead screw mechanism and tie rod are used to move the floor up and down, simulating the change in the flight altitude of the ground effect vehicle; the front fairing and rear fairing are used to rotate the ground effect vehicle model around the joint, simulating the change in the pitch angle of the ground effect vehicle.

7. The method for estimating the longitudinal coefficient of a ground effect vehicle as described in claim 4, characterized in that, The wind tunnel model simulates different flight attitudes by adjusting the pitch angle.

8. A ground effect vehicle aerodynamic characteristic analysis system, characterized in that, The longitudinal aerodynamic coefficient of the ground effect vehicle is estimated using the method for estimating the longitudinal coefficient of the ground effect vehicle according to any one of claims 1-7, and the stability calculation results are output. The system includes a wind tunnel model, which includes a floor. The floor is connected to the upper wall of the wind tunnel model via at least one tie rod, and a lead screw mechanism is provided at the connection point. A ground effect vehicle model is installed below the floor, and the lower part of the ground effect vehicle model is connected to a fairing installed on the lower wall of the wind tunnel model.

Images