A Method for Acquiring Transition Reynolds Number under Flight Conditions

Abstract

The invention relates to a transition Reynolds number acquisition method under the condition of flight. Firstly, shrinkage model test meeting the test similarity criterion is carried out in a ground wind tunnel to obtain a transition Reynolds number under the ground simulation condition; secondly, air-ground difference analysis is conducted, and the change data of the transition Reynolds number with an amplification factor N at different wall temperatures is given based on the flow stability theory; thirdly, the change law of the reference value of the transition Reynolds number with the walltemperature is obtained, and a wall temperature correction formula is obtained through curve fitting; fourthly, the change data of the transition Reynolds number with the amplification factor N afternormalization is obtained, and a noise correction formula is obtained; and finally, a unified extrapolation formula is formed, and a transition Reynolds number under the condition of flight is obtained through extrapolation based on a ground transition Reynolds number. The method has the advantage as follows: the transition test data is highly reliable and accurate, the cost of the method is muchlower than that of a method in which an association formula is obtained through test data fitting; and the data obtained by the stability theory is more regular, and the function relation is more accurate.

Description

Technical field [0001] The invention relates to a method for obtaining transition Reynolds number under flight conditions, which is used for the prediction of boundary layer transition criterion and belongs to the technical field of aerodynamics. Background technique [0002] Boundary layer transition refers to the transition from laminar flow to turbulent flow. Due to the different transport properties of mass, momentum and energy between laminar flow and turbulent flow, the friction and heat flow in turbulent state are 3-5 times that of laminar flow, showing the boundary The layer transition position has an important influence on the prediction of friction and heat flow. Friction and heat flow are important basis for aircraft design. Therefore, transition criterion is the basic and important basis for aircraft design. [0003] The traditional method of obtaining the transition criterion is by fitting a large amount of experimental data. This method firstly requires a large amou...

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Problems solved by technology

Firstly, this method requires a large amount of test data, so the obtained transition criterion is very expensive; secondly, these historical test data are very different due to the test conditions, etc. The data has a large dispersion, the data is difficult to fit simply, and the transition criterion itself is not accurate; finally, in the innovative design stage of the aircraft, due to the adoption of new shape and flight trajectory, the existing transition criterion is facing failure The problem

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