Determination of hot-wire position from a solid wall in an opaque channel

Hot-wire experiments sometimes require the position of the hot-wire probe with respect to a solid wall to be known, as is often the case with boundary layer flow measurements. However, optical access to determine the position of the wall visually may not always be available. The current paper describes a procedure to allow a hot wire to determine accurately the location of the solid wall with respect to any arbitrary reference position using the response of the hot wire when it approaches a solid wall under no flow conditions. An accurate probe-positioning system can then be used to position the probe with respect to this wall. The method is applied to both an aluminum wall and a Perspex wall, and both give consistent measurements with an accuracy of better than ?0.005?mm.