On the diodicity enhancement of multistage Tesla valves

Tesla valve is a particular check valve that can be used as a fluidic diode, but has no moving parts, and shows promising applications in macro- and microfluidic systems. Fluidic diode indicates that the inflow direction of a Tesla valve affects the pressure drop, allowing fluid to pass easily in one direction while presenting higher resistance in the reverse direction. Although previous studies have shown that the diode performance of such valves can be significantly improved by placing a series of valve units in a compact cascade, the reason is still unclear. In this study, the effect of the internal flow, especially the inflow status of each valve unit, on the diode characteristics of a multistage Tesla valve is investigated numerically and experimentally. Through a proper mathematic treatment, we derived the limiting diodicity in terms of the number of units and demonstrated that the diodicity enhancement of a multistage Tesla valve with its number of units was mainly due to the distorted inflow from subsequent units. To further verify this hypothesis, we elongated the space between subsequent units and found as expected the diodicity declined. The results indicate that distorted inflow can enhance the diodicity of a Tesla valve.