Spatially averaged dissipation rate in flow through submerged, double-layered vegetation

In this study, the experimental results of turbulent flow in a submerged, double-layered (an alternating combination of shorter and taller plants in a staggered arrangement) rigid vegetation are analyzed with the aim of estimating the turbulent kinetic energy (TKE) dissipation rate from the perspective of the velocity structure functions. The entire flow domain is divided into three layers: Lower interfacial sublayer (LISL) consists of shorter plants and lower portion of taller plants, upper interfacial sublayer (UISL) extends up to the top of the taller plants above the shorter plants, and the main flow layer is situated above the vegetation extending up to the free surface. The fundamental flow parameters, including streamwise velocity, Reynolds shear stress, and TKE, are analyzed using the double-averaging methodology. At the extremities of the LISL and UISL, the influence of two vegetation layers is prominent in the form of two inflection points in the double-averaged velocity profile. The inner and outer inflection points correspond to the local and global peaks in spatially averaged Reynolds shear stress and TKE profiles. The velocity structure functions of second-, third-, and mixed third-order are used to delineate the presence of the inertial subrange across the flow depth. The extent of the inertial subrange exhibits variability across the flow depth, indicating the impact of vegetation layers on the flow. Furthermore, the scaling laws are applied estimating the TKE dissipation rate and Taylor microscale for different vertical distances. Finally, by employing the extended self-similarity technique, the scaling exponents and their intermittencies are estimated.