Numerical solutions of forward-flight rotor flow using an upwind method

A finite-volume upwind algorithm for solving the three-dimensional Euler equations with a moving grid been has developed for computing helicopter forward-flight rotor flows. The computed pressure distributions and shock positions of high-speed rotor flow are compared with various experimental data as well as with other numerical results, and the agreement is encouraging. A comparison of quasisteady solutions with unsteady solutions reveals that when a shock occurs in the flowfield, the assumption of quasisteady flow may fail due to the time lag of the shock motion. Similarly, three-dimensional effects cannot be neglected. Sufficient subiterations for each time step are required to avoid numerical lag effects in using the present method. The redistribution of the residual due to the coordinate transformation is discussed. For high-order Monotone Upstream- Centered Conservation Law (MUSCL)-type schemes, a coordinate-independent solution can be obtained by interpolating primitive variables.