Validation of the Steady-State Hover Formulation for Accurate Performance Predictions

Abstract

This paper shows accurate predictions for hover performance regardless of planform geometry, blade tip Mach number or disk loading. To prove this statement, sensitivity analyses were performed along with performance predictions for four rotor designs. Planform effects were also studied, such as blade anhedral, showing the strong sensitivity of the rotor blade performance due to geometric features. The steady state solution methodology with imposed Froude boundary conditions is shown to give accurate results for relatively coarse grid sizes. This approach leads to reduced computational costs compared to time-dependent simulations. It is also recognised that given the current accuracy of the available experimental data, the use of more advanced CFD methods may not be fully justified. To advance the accuracy of modern CFD methods a more comprehensive experimental dataset is required. Nomenclature AR = aspect ratio, R/c r e f a = speed of sound, m/s C p = pressure coefficient, (p − p ∞ )/(1/2ρ(Ωr/R) 2 ) C f = skin friction coefficient, τ w /(1/2ρ(Ωr/R) 2 ) C Q = torque coefficient, Q/( ρ(ΩR) 2 πR 3 ) C T = thrust coefficient, T/( ρ(ΩR) 2 πR 2 ) c = rotor chord, m E = endurance, s FoM = figure of merit, C 3/2 T /( √ 2C Q ) k = turbulent kinetic energy, m 2 /s 2 M = Mach number, V ∞ /a ∞ M tip = blade tip Mach number, ΩR/a ∞ * PhD Student, CFD Laboratory, School of Engineering.

Numerical Analysis of HVAB and STAR Rotor Blades Using HMB3

“…The taper and sweep closely match the HVAB blade tip. The PSP rotor results in hover matched the experimental results as published by Jimenez-Garcia and Barakos [13] and Fitzgibbon et al [14], with the latter work comparing fixed and free transition results, and explaining in more detail the PSP blade results in level flight. The PSP rotor is very close to the HVAB planform, described in Section IV.…”

Numerical Simulation of Distributed Propulsion Systems Using Cfd

“…The Froude condition is using a potential-sink for the inflow and outflow instead of freestream values. This has been extensively validated and used in previous works [29,35]. The advantage of this method is that it uses the rotor thrust to compute the strength of the potential sink placed at the rotor origin, hence accelerating the convergence of the simulation.…”

Investigation of Wake Breakdown in Hover Using The HMB3 Solver

“…The simulations for this study are performed on a finer grid than used for typical hover performance engineering calculations [17]. The chimera technique is used, with all four blades modelled.…”