Drag prediction, decomposition and visualization in unstructured mesh CFD solver of TAS‐code

Abstract

SUMMARYThe accuracy of drag prediction in unstructured mesh CFD solver of TAS (Tohoku University Aerodynamic Simulation) code is discussed using a drag decomposition method. The drag decomposition method decomposes total drag into wave, profile, induced and spurious drag components, the latter resulting from numerical diffusion and errors. The mesh resolution analysis is conducted by the drag decomposition method. The effect of an advanced unstructured mesh scheme of U-MUSCL reconstruction is also investigated by the drag decomposition method. The computational results show that the drag decomposition method reliably predicts drag and is capable of meaningful drag decomposition. The accuracy of drag prediction is increased by eliminating the spurious drag component from the total drag. It is also confirmed that the physical drag components are almost independent of the mesh resolution and scheme modification.

Stochastic Drag Analysis via Polynomial Chaos Uncertainty Quantification

“…(In 3D cases, the induced drag component is also extracted.) 21) This detailed information on aerodynamic drag coefficients is considered beneficial for more advanced aerodynamic uncertainty quantification, as well as for robust and reliability design optimizations under uncertainty.…”

“…However, it is known that the majority of spurious drag is generated in a region around the leading-edge, which is outside of the boundary layer region. 19,21) Therefore, the spurious drag generated in the shock and viscous regions is generally insignificant. It has already been demonstrated that accurate drag prediction can be achieved by eliminating the spurious drag component.…”

“…It has already been demonstrated that accurate drag prediction can be achieved by eliminating the spurious drag component. 19,21) The advantages of the far-field drag breakdown method are that it can divide the entropy drag into the wave, viscous and spurious drag components, and can visualize the generated positions and the strength of the entropy drag in the flowfield, since the integrand of Eq. (24), r ÁF Ás; ÁH ð Þ , indicates the entropy drag production rate per unit volume.…”

“…(24), r ÁF Ás; ÁH ð Þ , indicates the entropy drag production rate per unit volume. 21) The domain decomposition of the flowfield is conducted based on the following shock and viscous detective functions. For detecting the shock region, the following function is used 28) :…”

“…These approaches are often referred to as the "Far-Field method." [17][18][19][20][21][22] In these advanced approaches, total drag can be decomposed into three physical components of wave, viscous and induced drag, and one spurious drag component. Furthermore, the drag source and its generated positions can be visualized in the flowfield using this approach.…”