A simplified model of a low speed large twostroke marine diesel engine cylinder is developed. The effect of piston position on the in-cylinder swirling flow during the scavenging process is studied using the stereoscopic particle image velocimetry technique. The measurements are conducted at different cross-sectional planes along the cylinder length and at piston positions covering the air intake port by 0, 25, 50 and 75 %. When the intake port is fully open, the tangential velocity profile is similar to a Burgers vortex, whereas the axial velocity has a wakelike profile. Due to internal wall friction, the swirl decays downstream, and the size of the vortex core increases. For increasing port closures, the tangential velocity profile changes from a Burgers vortex to a forced vortex, and the axial velocity changes correspondingly from a wake-like profile to a jet-like profile. For piston position with 75 % intake port closure, the jet-like axial velocity profile at a cross-sectional plane close to the intake port changes back to a wake-like profile at the adjacent downstream cross-sectional plane. This is characteristic of a vortex breakdown. The non-dimensional velocity profiles show no significant variation with the variation in Reynolds number.

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Received (Day Month Year) Revised (Day Month Year)Purpose-the purpose of this paper is to study the effect of piston position on the in-cylinder swirling flow in a simplified model of a large two-stroke marine diesel engine.Design/Methodology/Approach-Large Eddy Simulations with four different models for the turbulent flow are used: a one-equation model, a dynamic one-equation model, a localized dynamic one-equation model and a mixed-scale model. Simulations are carried out for two different geometries corresponding to 100 % and 50 % open scavenge ports.Findings-It is found that the mean tangential profile inside the cylinder changes qualitatively with port closure from a Lamb-Oseen vortex profile to a solid body rotation while the axial velocity changes from a wake-like profile to a jet-like profile. The numerical results are compared with particle image velocimetry measurements (?) and in general we find a good agreement.Limitations/implications-Considering the complexity of the real engine, we designed the engine model using the simplest configuration possible. The setup contains no moving parts, the combustion is neglected and the exhaust valve is discarded.Originality/value-Studying the flow in a simplified engine model, the setup allows studies of fundamental aspects of swirling flow in a uniform scavenged engine. Comparing the four turbulence models, the local dynamic one-equation model is found to give the best agreement with the experimental results.

SummaryWe present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the meshfree smoothed particle hydrodynamics method, but the present method introduces a mesh for efficient calculation of the pressure gradient, and laminar and turbulent diffusion. In addition, the mesh is used to remesh (reorganise uniformly) the particles to ensure a regular particle distribution and convergence of the method. The accuracy of the presented methodology is tested for a number of benchmark problems involving two-and three-dimensional Taylor-Green flow, thin double shear layer, and three-dimensional isotropic turbulence. Two models were implemented, direct numerical simulations, and Smagorinsky model. Taking advantage of the Lagrangian advection, and the finite difference efficiency, the method is capable of providing quality simulations while maintaining its robustness and versatility.

We present an implicit boundary particle method with background mesh adaptation. We use a Brinkman penalisation to represent the boundary of the domain and a remeshed particle method to simulate viscous flow with high Reynolds numbers. A penalty term is added to the Navier-Stokes equations to impose the boundary conditions. The boundary conditions are enforced to a specific precision with no need to modify the numerical method or change the grid, achieving diesel engine. The remeshed particle-mesh method coupled with Brinkman penalisation provides a good quality simulation and the results are in agreement with analytical or reference solutions.Many engineering applications require numerical simulations of viscous flows around complex geometries for which the body-fitted grid (BF) method [1], and the immersed boundary (IB) method [2, 3] are the two main approaches.The BF method proposes to generate grids associated with complex bound-5 aries. Consequently, boundary conditions are easily enforced. In order to achieve sufficiently accurate results for flows with high Reynolds numbers, a finer grid for the boundary layer is required. However, generating a good quality fine mesh can be cumbersome, and such meshes lead to substantial computational costs. In moving boundary cases, the simulation setup becomes more complex, 10 expensive as a result of the grid generation process, and the interpolation process of the solution to the new mesh at each computational time step creates projection errors. The BF method can thus be both complex to implement and computationally expensive. Peskin [4] introduced the IB method as a new approach to study the flow 15