The thermal characteristics of a hot wire in a near-wall flow

A two-dimensional numerical study is carried out to obtain the correction curve for the near-wall measurements by an infinitely long hot wire having been calibrated under free stream condition for the two extreme cases of isothermal and adiabatic wall conditions. Unlike previous studies particularly in experiments where the correction curve is primarily based on only the distance (h) between the wall and the wire expressed in wall units image, it is found that a second dimensionless parameter h0 (≡h/D) accounting for the effect of the hot wire diameter (D) is necessary to describe fully the overall near-wall correction curve. Our calculations also reveal a possible reason for the apparent discrepancy between the near-wall hot wire correction curves of Chew and Shi [Y.T. Chew, S.X. Shi, Wall proximity influence on hot-wire measurements, In: R.M.C. So, C.G. Speziale, B.E. Launder (Eds.), Near-Wall Turbulent Flows, Elsevier, Amsterdam, 1993, pp. 609–619] and Lange et al. [C.F. Lange, F. Durst, M. Breuer, Wall effects on heat losses from hot-wires. Int. J. Heat Fluid Flow 20 (1999) 34] next to a thermally non-conducting wall.