Vliv výpočetní sítě a modelu turbulence na CFD optimalizaci štěrbinové vztlakové klapky

Computational mesh and rans model of turbulence sensitivity in CFD optimization of slotted flap

lecture

en

As powerful and relatively fast and cheap tools, CFD solvers are used for solution of wide range of problems in the aerodynamics including the search for optimal position of slotted flap. If relative difference between CFD result and real behavior of the flow varies strongly with the flap configuration, predicted optimum may vary from the real one as well. Therefore a test case focused on estimation of this type of error was conducted. This article presents results of computed 2D aerodynamic of NACA 66(2)-216 airfoil with 25% slotted flap deployed and located at 25 different positions. Combination of unstructured and hybrid computational meshes with total number of elements ranging from 79 to 330 thousands and three RANS models of turbulence were applied. For each model of turbulence a consistency of results with respect to the mesh density is discussed in the article and compared to the general recommendations. Finally, the data obtained from CFD solution were validated against the wind tunnel measurement and conclusions were made.

CFD řešiče, jakožto výkonné a relativně dostupné nástroje pro výpočty v oblasti aerodynamiky, jsou často používány ke zjišťování optimální polohy štěrbinové vztlakové klapky. Problém nastává, mění-li se přesnost CFD výpočtů v závislosti na aktuální konfiguraci klapky, protože potom se vypočítaná a skutečná optimální poloka klapky může lišit rovněž. Byla proto zpracována validační úloha zaměřená na zjištění tohoto druhu chyby výsledků. Popsány jsou výsledky 2D úlohy s geometrií profilu NACA 66(2)-216 se štěrbinovou klapkou ve 25 různých pozicích. Výpočty probíhaly s různými modely turbulence a sítěmi různých hustot (79tis. až 330tis. buněk). Výsledky jsou porovnávány navzájem a také se známými obecnými doporučeními týkajícími se 2D CFD výpočtů profilu se štěrbinovou klapkou. Porovnání bylo provedeno i s výsledky měření v aerodynamickém tunelu.

As powerful and relatively fast and cheap tools, CFD solvers are used for solution of wide range of problems in the aerodynamics including the search for optimal position of slotted flap. If relative difference between CFD result and real behavior of the flow varies strongly with the flap configuration, predicted optimum may vary from the real one as well. Therefore a test case focused on estimation of this type of error was conducted. This article presents results of computed 2D aerodynamic of NACA 66(2)-216 airfoil with 25% slotted flap deployed and located at 25 different positions. Combination of unstructured and hybrid computational meshes with total number of elements ranging from 79 to 330 thousands and three RANS models of turbulence were applied. For each model of turbulence a consistency of results with respect to the mesh density is discussed in the article and compared to the general recommendations. Finally, the data obtained from CFD solution were validated against the wind tunnel measurement and conclusions were made.

štěrbinová vztlaková klapka, CFD, aerodynamicý tunel, validace, výpočetní síť, model turbulence

slotted flap, CFD, wind tunnel, validation, computational mesh, model of turbulence

14.09.2016

konference Research and Education in Aircraft Design 2016, Varšava, Polsko