Research On Wind Tunnel Wall Correction Methods For Helicopter Experiment

Wind tunnel experiment has an irreplaceable role in helicopter development, but there will besignificant wall interference when aerodynamic tests of the rotor are carried out in the wind tunnel,measurement results must be corrected to reflect aerodynamic characteristics of the free flight state.Wind tunnel wall correction methods for helicopter experiment are analyzed in this article, potentialflow theory and momentum source model are used to build wind tunnel wall correction methods forisolated rotor and rotor/fuselage combination model.First, computational formulas of wind tunnel wall interference are derived based on the potentialflow theory, solution method of wall interference factor is established, a wall interference correctionprogram is written. The test results of DNW wind tunnel is used to verify accuracy of the program.Then, momentum source method is used for wind tunnel wall interference correction ofhelicopter experiment. Momentum source term is used to substitute the role of rotor blades onadjacent flow field, in order to build a numerical method for rotor flow field solution. The rotordownwash flow field in hover and forward flight conditions is calculated, calculation results arecompared with the experiment data to prove the accuracy of this method. The isolated rotordownwash flow field under the impact of wind tunnel wall is simulated using the momentum sourcemethod. The rotor shaft angle correction is obtained and compared with the calculation result ofpotential flow method. The momentum source method is used for wind tunnel wall correction of thewhole flow field. Wall interference is calculated under different flow speed and wind tunnel aspectratio.At last, the rotor/fuselage interference flow field under forward flight condition is simulatedusing the momentum source method. Pressure distribution of the fuselage surface is calculated andcompared with experiment results of Langley Research Center to verify the accuracy of this method.Rotor/fuselage interference flow field with and without wind tunnel wall is calculated to analyze theinfluence of wind tunnel wall on pressure distribution of the fuselage surface in the condition ofcombined model wind tunnel test.