In LSCI, the link between speckle contrast and flow can only be made if the flow distribution is known. However, the actual flow distribution of biological fluid is often unknown. Early work has assumed the flow of blood to exhibit either purely unordered (Lorentzian) or ordered (Gaussian) flow.2,15,16 Theoretically, a Lorentzian velocity distribution is only appropriate for Brownian motion (purely random flow). Conversely, a Gaussian velocity distribution is technically only appropriate for purely ordered flow. In practical situations, it is likely that the true flow model is a mixture between the Lorentzian and Gaussian line shapes. In laser engineering terms, the convolution between these two line shapes is a Voigt profile, frequently referred to as a rigid-body model.3 Because assumptions are made to describe the fluid velocity distribution, the unambiguous quantification of flow velocity from contrast values is not yet possible. To model the fluid velocity distribution with this system, in addition to controlling the temporal decorrelation rate of the speckle images, we produce speckle sequences that decorrelate following a user defined function. We demonstrate this by producing speckle sequences that result in calculated contrast values that follow both Gaussian and Lorentzian distributions.1 However, it should be noted that any desired function can be used to mimic whatever flow model is desired. The experimental contrast values were compared to the theoretical values as a function of the ratio of the speckle decorrelation time, , and the integration time, . Here, the speckle decorrelation time, , was predetermined by the realization number of the generated phase screens, and the integration time, , was determined by the number of summed frames. The results are shown in Fig. 7 which displays a comparison of theoretical and experimental results. For the experiments with varied intensity, 30 phase screens assuming a Gaussian decorrelation pattern were summed to ensure the LSC images were sampled and summed to appropriately mimic contrast values seen when imaging experimental dynamic speckle with a finite exposure time.