SENSING VOLUME AND BIASING CORRECTIONS FOR DUAL COUNTER LDA PROCESSORS

Most operable Laser Doppler Anemometry (LDA) systems employ the fringe mode geometrical configuration with a counting type signal processor. The fringes are contained within an ellipsoid volume, which is commonly described as the sensing volume of the LDA. Generally, the dimensions of the focusing volume are determined from the waist diameter of the beams and their intersection angle. However, the electronic processing system exerts several constraints upon the size of the focusing volume. In this study we will address ourselves to the constraints of the dual counter processing system, which is based on the individual realization mode of the LDA. Correction equations will be derived for the sensing volume and the individual realization biasing and applied to two-component flow fields, measured by a one-dimensional LDA system.