Experimental Study of the Plunging Motion with Unsteady Wind Tunnel Wall Interference Effects

Abstract

A series of experiments were carried out to investigate unsteady behavior of the flow field as well as the boundary layer of an airfoil oscillating in plunging‐type motion in a subsonic wind tunnel. The measurements involved surface‐mounted hot films complimented with surface pressure. In addition, wind tunnel wall pressure distribution was acquired to furnish a baseline for the wall interference corrections. The airfoil is the section of a 660‐kW wind turbine blade. The experiments were conducted at a Reynolds number of 0.42 million, and over two reduced frequencies of k = 0.06 and 0.085, at prestall, nearstall, and poststall regions. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces of the model. The plunging displacements were transformed into the equivalent angle of attack. The surface hot‐film measurements provided information about the boundary‐layer events. The boundary‐layer transition occurred via a laminar separation bubble. Variations of the surface pressure coefficients and aerodynamic loads with the equivalent angle of attack showed strong sensitivity to the reduced frequency and the mean angles of attack. The wall pressure distribution was affected by the model oscillation especially the region underneath the model.

Time-Frequency Analysis and Transitional Boundary Layer Investigation over a Pitching Airfoil

“…This leads to further delay in transition onset during the pitchup. This is similar to the effect of reduced frequency on the load hysteresis loop that has been previously reported [9,15,16,19]. Also, for oscillation beyond αss (αm = 10 deg), the hysteresis loop for transition onset locations is larger.…”

“…Also, a new RMS parameter is defined based on the time-frequency analysis of the hot-film signals which could be employed for unsteady transition and relaminarization onset detection. This work follows the previous investigations of Soltani and co-workers [15][16][17][18][19] on explaining the aerodynamic behavior of the current airfoil model in steady and unsteady conditions.…”

Experimental Result Comparisons of Curve Fitting Algorithms on Fluid Path Lines Modeling in Strengthen Grinding Flow Field

“…More relevant technical progresses about the influence mechanism of turbulence modeling operation can also be found from Ref. [12][13][14] When discussing the result comparison of turbulence modeling algorithms to be investigated in this article, we can see that more researchers began paying their high attentions on this new theoretical domain. For example, Hong 15 have used fuzzy measures for a correlation coefficient of numbers under TW (the weakest t-norm)-based arithmetic operations.…”

A Novel Experimental Setup for Multiparameter Aeroelastic Wind Tunnel Tests

“…Aeroelastic experiments in wind tunnels are an essential part of the science and practice of aeroelasticity. They are conducted in different areas, for example envelope clearance test for new aircraft designs, active control and suppression of aeroelastic responses, unsteady aerodynamics, and flutter and divergence behavior investigation . For these purposes, different models and mounting systems were used, for example semi‐span models cantilever mounted to the tunnel sidewall, full‐span models mounted on a cable system, and rigid wings mounted on a two‐degree of freedom (2‐DOF) mounting system.…”