, and is distinctive in that the subgrid scale turbulence is parameterized by a k-l model. The length scale of turbulence l is proportional to the grid size and the turbulence energy k is obtained from the solution of the turbulence energy transport equation. An operator splitting method, which splits the solution procedure into advection, di usion and pressure propagation steps, is employed so that di erent numerical schemes can be used for the solution of di erent physical processes. The model has been applied to simulate open channel ow with transverse shear produced by vegetation drag. Some organized large eddies were found in the interface between the vegetated and non-vegetated regions and the organized structure clearly has a life cycle. At the interface the transverse velocity proÿle exhibits a steep gradient, which induces signiÿcant mass and momentum exchange, acts as a source of vorticity, and generates high Reynolds stresses. The logarithmic vertical velocity variation becomes uniform in the vegetated domain. The agreement between the numerical results and the experimental data (Tsujimoto and Kitamura, KHL Progressive Report '92, Hydrology Laboratory, Kanazawa University, Japan, 1992; 21) is satisfactory. The present k-l LES model is proven to be a useful tool for engineering applications, as it can simulate the dynamic development of large eddies and the associated intermittent turbulence.

In this paper, an unstructured mesh Arbitrary Lagrangian-Eulerian (ALE) incompressible flow solver is developed to investigate the aerodynamics of insect hovering flight. The proposed finite-volume ALE Navier-Stokes solver is based on the artificial compressibility method (ACM) with a high-resolution method of characteristics-based scheme on unstructured grids. The present ALE model is validated and assessed through flow passing over an oscillating cylinder. Good agreements with experimental results and other numerical solutions are obtained, which demonstrates the accuracy and the capability of the present model. The lift generation mechanisms of 2D wing in hovering motion, including wake capture, delayed stall, rapid pitch, as well as clap and fling are then studied and illustrated using the current ALE model. Moreover, the optimized angular amplitude in symmetry model, 45°, is firstly reported in details using averaged lift and the energy power method. Besides, the lift generation of complete cyclic clap and fling motion, which is simulated by few researchers using the ALE method due to large deformation, is studied and clarified for the first time. The present ALE model is found to be a useful tool to investigate lift force generation mechanism for insect wing flight.

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A novel physiologically based algorithm (PBA) for fast CFD computation of Flow Fractional Reserve (FFR) in Coronary Artery Trees (CATs) is proposed and developed, which, unlike traditional methods, is based on the extension of the Murray’s law for blood vessels at the outlets and extra inlet conditions prescribed alternatively and iteratively. The PBA is then implemented in both SimVascular and Ansys CFD for testing and validation. For validation purpose, 3D models of CATs are built by using their CT images and computational meshes generated for mesh convergence study. Results obtained are then compared with Invasive Coronary Angiographic (ICA) data for validation and evaluation of its accuracy and computational efficiency. It is found that discrepancies between experimental and calculated values of pressure and flow rate at the inlet were less than 0.1% at the end of the 10th round of iteration or less. Further validation shows that the difference between estimated and experimental FFR agree with each other with a maximum difference of 1.62% after convergence is achieved. The PBA is found to be a robust patient-specific and physiologically sound method that can be a good alternative to the existing Lumped Parameter Model (LPM) which is based on empirical scaling correlations using limited population-averaged data and requires nonlinear iterative computation for convergence.