Reynolds number effect correcting method of zero lift-drag force coefficient

Abstract

The invention discloses a Reynolds number effect correcting method of a zero lift-drag force coefficient. The method comprises the steps of: obtaining a zero lift attack angle [alpha]0 of an aircraft at a Mach number according to wind tunnel experiment data; calculating an actual Reynolds number ReH under each sea level altitude H based on an size and configuration of a product, and calculating a drag force coefficient CxH at the Mach number and at each altitude H when the attack angle [alpha] equals to [alpha]0, by a CFD method; increasing the Reynolds number of a blowing wind tunnel at the Mach number to the Reynolds number Re corresponding to the practical aircraft size according to a model scale, interpolating the Reynolds number Re with ReH values at different altitudes H at the step b to obtain flight altitude H wind tunnel experiment corresponding to the Re wind tunnel experiment, and calculating a drag force coefficient Cx0 of the aircraft when the attack angle [alpha] equals to [alpha]0 in the altitude H wind tunnel experiment; and obtaining a corrected value of the zero lift-drag force at the Mach number and at each flight altitude H. The Reynolds number effect correcting method of the zero lift-drag force coefficient is used for a small aspect ratio aircraft and is applicable to zero lift-drag coefficient correction.

Description

technical field [0001] The invention relates to a Reynolds number effect correction method for zero-lift drag coefficient. Background technique [0002] Reynolds number is an important dimensionless parameter in fluid mechanics, which mainly characterizes the ratio of inertial force to viscous force. The influence of Reynolds number permeates almost all fields where fluid flow exists, and has varying degrees of influence on complex flows such as transition, flow separation, and shock wave / boundary layer interference. The Reynolds number is closely related to the aerodynamic performance of the aircraft, such as low-speed high-lift characteristics, drag characteristics, and maximum lift characteristics. Therefore, the Reynolds number simulation capability and the Reynolds number impact assessment of production wind tunnels have always been concerned by the industry. [0003] From the present point of view, the impact assessment of Reynolds number mainly takes wind tunnel tes...

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Problems solved by technology

[0003] From the present point of view, the impact assessment of Reynolds number mainly takes wind tunnel test as the main method, generally by increasing the density of airflow, reducing the temperature of airflow or both to carry out variable Reynolds number test, but the test equipment and related Restricted by factors, most production wind tunnels have a narrow range of Reynolds numbers

However, limited by the size of the wind tunnel, the general wind tunnel test models are scaled down from the actual model of the original product, especially for large aircraft in conventional production wind tunnels. The flight Reynolds number is 1 to 2 orders of magnitude lower than that, which makes the aerodynamic data measured by the wind tunnel very different from the actual flight conditions. The problem of Reynolds number correction under certain conditions, or the extrapolation of wind tunnel scale model test results has always been the focus of attention of aircraft designers

However, in actual engineering treatment, it is believed that the Reynolds number has little effect on the slope of the curve of lift and pitching moment with the angle of attack. In the design, the wind tunnel test data of the low Reynolds number of the scale model is directly used, and only the drag coefficient is corrected.

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