EXAMINATION OF THE FLOW AROUND A HOT-WIRE PROBE USING PARTICLE IMAGE VELOCIMETRY

Previous work has shown that the k(2) term in the effective cooling ve locity equation for inclined hot-wires can become negative under certa in probe configurations and wire length-to-diameter ratios. It was hyp othesised that this was due to a downwash component of velocity along the wire when prong interference effects were expected to be minimal. Direct measurements of the flow around a typical hot-wire probe using digital particle image velocimetry have shown that this downwash veloc ity component does exist, leading to negative values of k(2) as calcul ated from the angle of deviation from the free stream.