Analysis of the results of the study of thermal flows on the surfaces of aircraft models during supersonic gas flow


Аuthors

Sidnyaev N. I.*, Battulga E.

Baumann Moscow State Technical University, 105005, Moscow, 2nd Baumanskaya St., b. 5, c. 1

*e-mail: sidn_ni@mail.ru

Abstract

An experimental approach to the study of the distribution of heat fluxes on the surface of aircraft during supersonic gas flow is presented. The main focus is on the statistical analysis of heat flux measurement results under different flow parameters to obtain regression models. It is postulated that in turbulent flow conditions in the boundary layer, surface mass transfer leads to a decrease in heat fluxes. An analytical review is presented. It is postulated that when designing modern high-speed aircraft, it is of particular importance to correctly assess and take into account the effect of gas mass transfer different in intensity and distribution over the surface of the body in the wall layer on the distributed and integral aerodynamic characteristics of aircraft. The process of sublimation of heat-protective material is described. It is noted that under turbulent flow conditions in the boundary layer, surface mass exchange leads to a decrease in heat flows to the wall due to changes in the velocity and temperature profiles in the boundary layer. The values of the turbulent transfer coefficients depend on the results of measurements of such flow parameters as gradients of average speed and temperature values. Ratios expressing turbulent viscosity coefficient and turbulent Prandtl number are obtained. In the calculations, the interleaving coefficient is used, which takes into account the fact that when approaching the outer boundary of the boundary layer, turbulence becomes intermittent, i.e. the flow is turbulent only part of the entire time. The boundary between the inner and outer regions of the boundary layer is determined from the condition of continuity of the turbulent viscosity coefficient; at a distance from the wall to this boundary, the formula for the turbulent viscosity coefficient for the inner region is applied until equality is fulfilled. Various ratios for the turbulent Prandtl number have been proposed. The dependence of the surface friction coefficient on various factors (flow rate, pipe thickness, etc.) has been established. The adequacy of the constructed regression model was checked. It is noted that the pressure gradient cannot significantly affect the calculated results for the rough surface. It is interpreted that the calculation method allows obtaining sufficiently accurate results for a flow with a pressure gradient on a smooth surface. Roughness causes a change in the boundary condition on the wall, but does not affect the appearance of the calculation formulas used in the outer part of the layer.

Keywords:

analysis, heat flux, surface, model, flow, supersonic

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