Mehmet Sahin

• PhD
• Professor at Istanbul Technical University

The high-lift Japan Aerospace Exploration Agency (JAXA) standard model (HL-JSM) has been numerically analyzed in order to further validate the HEMLAB code for realistic aircraft configurations. The numerical algorithm is based on highly efficient edge-based data structure for a vertex-based finite volume algorithm on hybrid meshes. The data pattern...

This article presents the numerical analysis of the wing-body configuration of the NASA Common Research Model (CRM) within the context of the 7th AIAA CFD Drag Prediction Workshop (DPW-7), using the Reynolds-averaged Navier-Stokes flow solver HEMLAB. Estimating the effect of shock-induced separation on the aerodynamic force, moment coefficients, an...

This work presents delta wing simulations using two different geometries: Delta wing geometry provided in the International Workshop on High-Order CFD Methods and the Sydney Standard Aerodynamic Models (SSAM) for a generic fifth-generation high-performance aircraft. The purpose of the study is to accurately compute the lift and drag coefficients of...

HEMLAB algorithm has been applied to the NASA High-Lift Common Research Model (CRM-HL) provided in Vth AIAA CFD High Lift Prediction Workshop in order to investigate mesh convergence behavior of aerodynamic loads as well as its pre-and post-stall characteristics at high angles of attack. The numerical method is based on a vertex based finite volume...

Capabilities of In-house HEMLAB solver is extended by implementing an ALE approach. Developed algorithm is validated on 2D heaving and pitching NACA0012 cases proposed under HiOCFD4. Then, it is employed to asses the hover performance of S-76 main rotor. Since the rotor problems requires high resolution grids, adaptive mesh refinement is exploited...

Recently, a development over the open-source and density-based solver (HiSA) has been realized to include the ability to solve the rotorcraft flows over the rotating frame of reference, and this development has been validated for cases at the transonic regime. In the present study, the developed code's capability to solve rotorcraft flows at the su...

Rotor analysis poses numerous challenges due to complex flow phenomena, intricate geometries, strong vibrations, and shock waves. Traditional blade element theories fall short in accurately capturing sharp velocity gradients and vorticities in rotating flows, necessitating high-fidelity Computational Fluid Dynamics (CFD) tools. This study focuses o...

Capabilities of In-house HEMLAB solver is extended by implementing an ALE approach to solve rigid grid motion and is employed to asses the hover performance of S-76 main rotor. In the study, firstly, we verified our algorithm on baseline cases proposed under HiOCFD4 workshop. Then, we performed Euler simulations of S-76 main rotor with swept-tapere...

View Video Presentation: https://doi.org/10.2514/6.2022-3809.vid The NASA High-Lift Common Research Model (CRM-HL) has been investigated using the HEMLAB algorithm in order to numerically predict stall characteristics at high angle of attacks. The numerical method is based on a vertex based finite volume method on hybrid meshes using the quad- and...

Biplane configuration of pure plunging airfoils is investigated in terms of vortex dynamics both experimentally and numerically by utilizing particle image velocimetry and unstructured finite volume solver of incompressible unsteady Navier–Stokes equations. Experiments are carried out to disclose the vortex shedding and interaction mechanisms for v...

View Video Presentation: https://doi.org/10.2514/6.2022-1319.vid Solving a flow around a rotor via CFD techniques is still very expensive due to the complex behaviours of the air flow around a rotor. This study attempts to analyze the S-76 main rotor configuration with swept-tapered tip in the hover position. The SU2 software is utilized with an an...

The arbitrary Lagrangian Eulerian (ALE) framework presented in Sahin and Guventurk, International Journal for Numerical Methods in Engineering (2017) has been extended to simulate three‐dimensional immiscible multiphase fluid flows. The div‐stable side centered unstructured finite volume formulation is used for the discretization of the incompressi...

An efficient edge based data structure has been developed in order to implement an unstructured vertex based finite volume algorithm for the Reynolds-averaged Navier-Stokes (RANS) equations on hybrid meshes. In the present approach, the data structure is tailored to meet the requirements of the vertex based algorithm by considering data access patt...

In this study, the NASA Concept 25D with Flow-Through Nacelle (C25F) proposed in the AIAA Sonic Boom Workshop has been studied in two different aspects. First part of this paper is about validating the vertex based finite volume algorithm named HEMLAB for the selected geometry in terms of aerodynamic forces and pressure signatures. The HEMLAB algor...

The hover analysis using CFD tools have been gaining popularity since CFD techniques and soft-wares became essential tools to achieve high accuracy results on the existing complex geometries and, also, future geometries. However, solving a flow around a rotor is still very expensive due to the complex behaviours of the air flow around a rotor. This...

During the reentry phase, the earth atmosphere represents a relatively dense fluid medium and a reentry vehicle has to follow a very narrow re-entry corridor in order to have a safe landing. If the vehicle strays above the corridor, it may skip out and back to the cold space environment. If it strays below the corridor, it may burn up and/or experi...

The high-lift JAXA Standard Model (HL-JSM) has been numerically analyzed in order to further validate the HEMLAB code for realistic aircraft configurations. The numerical algorithm is based on highly efficient edge-based data structure for a vertex based finite volume algorithm on hybrid meshes. The data pattern is arranged to meet the requirements...

The experimental and numerical computational investigation of co-axial rotor performance has been increased over the past decade in order to understand complex interactions in co-axial rotor flows to improve design of unmanned-aerial vehicles. Nevertheless, the issues related rotor aerodynamic performance, wake interactions, etc. are not well under...

An efficient edge based data structure has been developed in order to implement a compress-ible Navier-Stokes solver based on a vertex based finite volume algorithm on unstructured hybrid meshes in two-and three-dimensions. In the present approach, the data structure is tailored to meet the requirements of the algorithm by considering data access p...

A novel numerical algorithm has been developed to solve the incompressible resistive magnetohydrodynamics (MHD) equations in a fully coupled form. The numerical method is based on the face centered unstructured finite volume approximation, where the velocity and magnetic field vector components are defined at the center of edges/faces, meanwhile th...

An integrated simulation of a Drosophila wing–body combination in hovering flight has been carried out in order to analyze the Lagrangian and Eulerian coherent structures. A parallel unstructured finite volume method based on an arbitrary Lagrangian–Eulerian (ALE) formulation has been initially validated for a flapping rectangular plate and then em...

A parallel monolithic uid-structure interaction (FSI) algorithm presented in [Eken and Sahin, A parallel monolithic algorithm for the numerical simulation of large scale uid structure interaction problems. International Journal for Numerical Methods in Fluids, 80:687-714, (2016)] has been used to investigate the deformation of red blood cells (RBCs...

A parallel fully‐coupled (monolithic) fluid‐structure interaction (FSI) algorithm has been applied to the deformation of red blood cells (RBCs) in capillaries, where cell deformability has significant effects on blood rheology. In the present FSI algorithm, fluid domain is discretized using the side‐centered unstructured finite volume method based...

An integral equation approach based on bi-cubic Hermite surfaces has been proposed to solve the three-dimensional complex Stokes flow problems. The numerical solutions are obtained by utilizing the boundary collocation method as well as the continuous distribution of Stokeslets, which are the fundamental solutions of the steady Stokes equations. Th...

The body of your abstract belongs here. ICCFD is the outcome of the merger of two important

An efficient edge based data structure has been proposed for the implementation of vertex based finite volume formulation. In the present approach, the quad-edge and halfedge data structures are redesigned and simplified in order to fit requirements of the cell-vertex centered finite volume methods. The present data structure is not limited with tr...

An arbitrary Lagrangian Eulerian (ALE) framework, which combines the advantages of both Lagrangian and Eulerian methods, is presented to solve incompressible multiphase flow problems. The incompressible Navier-Stokes equations are discretized using the side-centered unstructured finite volume method, where the velocity vector components are defined...

A parallel fully-coupled numerical algorithm has been developed for the fluid-structure interaction problem in a cerebral artery with aneurysm. For the fluid part of the problem, an Arbitrary Lagrangian-Eulerian formulation based on the side-centered unstructured finite volume method is employed for the governing incompressible Navier-Stokes equati...

A numerical algorithm has been developed to solve the incompressible magneto-hydrodynamics (MHD) equations in a fully coupled form. The numerical approach is based on the side centered finite volume approximation where the velocity and magnetic filed vector components are defined at the center of edges/faces, meanwhile the pressure term is defined...

A parallel adaptive mesh refinement algorithm has been incorporated into the side-centered finite volume method [Sahin, A stable unstructured finite volume method for parallel large-scale viscoelastic fluid flow calculations. J. Non-Newtonian Fluid Mech., 166 (2011) 779–791] in order to obtain highly accurate numerical results for viscoelastic flui...

The flow pattern around a NACA0012 airfoil undergoing harmonic plunging motion corresponding to the deflected wake phenomenon reported by Jones and Platzer (Exp Fluids 46:799–810, 2009) is investigated in detail using direct numerical simulations. An arbitrary Lagrangian–Eulerian formulation based on an unstructured side-centered finite volume meth...

The parallel large-scale unstructured finite volume method based on an Arbitrary Lagrangian-Eulerian (ALE) formulation has been developed in order to investigate the near wake structure of Drosophila flight. The numerical algorithm is based on side-centered finite volume method where the velocity vector components are defined at the mid-point of ea...

A novel parallel monolithic algorithm has been developed for the numerical simulation of large-scale fluid structure interaction problems. The governing incompressible Navier-Stokes equations for the fluid domain is discretized using the Arbitrary Lagrangian-Eulerian formulation based side-centered unstructured finite volume method. The deformation...

The parallel large-scale unstructured finite volume method based on an Arbitrary Lagrangian-Eulerian (ALE) formulation in Erzincanli and Sahin (2013) has been employed in order to investigate the effects of the wing kinematics on the near wake topology produced by a pair of flapping Drosophila wings in hover flight. The three-dimensional wing shape...

A parallel fully-coupled approach has been developed for the fluid-structure interaction problem in a cerebral artery with aneurysm. An Arbitrary Lagrangian-Eulerian formulation based on the side-centered unstructured finite volume method [2] is employed for the governing incompressible Navier-Stokes equations and the classical Galerkin finite elem...

The parallel large-scale unstructured nite volume method algorithm Visco-Solve has been extended for dynamic mesh adaptation using a template based mesh adaptation technique with conservative remapping. The dynamic mesh adaptation is carried out by implementing a template based conformal mesh renement/coarsening for quadrilateral and hexahedral ele...

An Arbitrary Lagrangian-Eulerian (ALE) formulation based on the unstructured finite volume method is proposed for solving moving boundary problems with large displacements and rotations. The numerical method is based on the side-centered arrangement of the primitive variables that does not require any ad-hoc modifications in order to enhance pressu...

The current article presents a new numerical algorithm based on the Arbitrary Lagrangian-Eulerian (ALE) formulation for a fully coupled solution of the large-scale fluid-structure interaction (FSI) problems where the fluid is modeled by the incompress-ible Navier-Stokes equations and the structure is modeled by the St. Venant-Kirchhoff model. The g...

An arbitrary Lagrangian-Eulerian approach has been de-veloped in order to investigate the near wake structure of Drosophila flight. The numerical algorithm based on side-centered finite volume method where the velocity vector com-ponents are defined at the mid-point of each cell face while the pressure is defined at the element centroid. An efficie...

The parallel large-scale unstructured finite volume method proposed in [Sahin, A stable unstructured finite volume method for parallel large-scale viscoelastic fluid flow calculations, J. Non-Newtonian Fluid Mech. 166 (2011) 779–791] has been applied to investigate the three-dimensional creeping flow of an Oldroyd-B fluid past a confined circular c...

Dynamic stall calculations were carried out for an airfoil with a dynamically deformed leading-edge (DDLE) shape at a freestream Mach number of 0.3. The surface deformations were done about a baseline NACA 0012 airfoil, effectively increasing the airfoil leading-edge radius and thickness at high angles of attack. It was found that the DDLE airfoil...

A parallel large-scale unstructured finite volume algorithm based on arbitrary Lagrangian- Eulerian (ALE) formulation has been developed in order to investigate Drosophila flight. The numerical algorithm based on side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face while the pressure...

Submitted for the DFD12 Meeting of The American Physical Society Sorting Category: 4. (C) Numerical Simulation of Drophila Flight Based on Ar-bitrary Langrangian-Eulerian Method 1 BELKIS ERZINCANLI, MEHMET SAHIN, Istanbul Technical University — A parallel unstruc-tured finite volume algorithm based on Arbitrary Lagrangian Eulerian (ALE) method has...

A fully coupled numerical algorithm has been developed for the numerical simulation of large-scale fluid structure interaction problems. The incompressible Navier-Stokes equations are discretized using an Arbitrary Lagrangian-Eulerian (ALE) formulation based on the side-centered unstructured finite volume method. A special attention is given to sat...

A new stable unstructured finite volume method is presented for parallel large-scale simulation of viscoelastic fluid flows. The numerical method is based on the side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face, while the pressure term and the extra stress tensor are defined at e...

An arbitrary Lagrangian-Eulerian (ALE) method based on the side-centered unstructured finite volume method is described for large-scale simulation of moving boundary problems in a fully coupled form. The numerical method based on side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face w...

A new stable unstructured finite volume method is presented for parallel large-scale simulation of viscoelastic fluid flows. The numerical method based on side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face, while the pressure term and the extra stress tensor are defined at element...

A new geometrically conservative arbitrary Lagrangian-Eulerian (ALE) formulation is presented for the moving boundary problems in the swirl-free cylindrical coordinates. The governing equations are multiplied with the radial distance and integrated over arbitrary moving Lagrangian-Eulerian quadrilateral elements. Therefore, the continuity and the g...

This manuscript briefly describes a parallel unstructured finite volume method for large-scale simulation of viscous fluid flows in a fully coupled form. The numerical method based on side-centered finite volume method where the velocity vector components are defined at the mid-point of each cell face while the pressure is defined at the element ce...

The thrust-generating mechanism of a prolate hydromedusa Sarsia tubulosa and an oblate hydromedusa Aequorea victoria was investigated by solving the incompressible Navier-Stokes equations in the swirl-free cylindrical coordinates. The calculations clearly show the vortex dynamics related to the thrust-generating mechanism, which is very important f...

A new geometrically conservative arbitrary Lagrangian–Eulerian (ALE) formulation is presented for the moving boundary problems in the swirl-free cylindrical coordinates. The governing equations are multiplied with the radial distance and integrated over arbitrary moving Lagrangian–Eulerian quadrilateral elements. Therefore, the continuity and the g...

A parallel unstructured finite volume method is presented for analysis of the stability of two-dimensional steady Oldroyd-B fluid flows to small amplitude three-dimensional perturbations. A semi-staggered dilation-free finite volume discretization with Newton’s method is used to compute steady base flows. The linear stability problem is treated as...

Entangled polymer melts exhibit a variety of flow instabilities that limit production rates in industrial applications. We study one such flow instability, in a contraction‐expansion geometry, through both experiment and numerical calculation. The experiments investigate the flow of monodisperse linear polystyrenes in a multi‐pass rheometer, and we...

Industrial processes involving co-extrusion of multiple fluids to produce multi-layered products are rife with instabilities. We consider a simple indicative instance of co-extrusion, in which there is only a single fluid involved in the flow, but two different channel branches impose differing flow histories on it. The channels merge and, ideally,...

Entangled polymer melts exhibit a variety of flow instabilities that limit production rates in industrial applications. We present both experimental and computational findings, using flow of monodisperse linear polystyrenes in a contraction-expansion geometry, which illustrate the formation and development of one such flow instability. This viscoel...

Low Reynolds number aerodynamics is important for various applications including micro-aerial vehicles, sailplanes, leading edge control devices, high-altitude unmanned vehicles, wind turbines and propellers. These flows are generally characterized by the presence of laminar separation bubbles. These bubbles are generally unsteady and have a signif...

Low Reynolds number aerodynamic flows are important for various applications including micro-arial vehicles, sailplanes, leading edge control devices, high-altitude vehicles and wind turbines. These flows are generally characterized by the presence of laminar separation bubbles. These bubbles are generally unsteady and have a significant effect on...

The dilation-free semi-staggered finite volume method presented in Int. J. Numer. Meth. Fluids 49 (2005) 959-974 has been extended for the numerical solution of viscoelastic fluid flows on all-quadrilateral(2D)/hexahedral(3D) meshes. The velocity components are defined at element node points, while the pressure term and the extra stress tensor are...

A new semi-staggered finite volume method is presented for the solution of the incompressible Navier–Stokes equations on all-quadrilateral (2D)/hexahedral (3D) meshes. The velocity components are defined at element node points while the pressure term is defined at element centroids. The continuity equation is satisfied exactly within each elements....

The present paper represents, as far as we are aware, the first linear stability analysis for inertial flows of a viscoelastic fluid around a bluff body. Our particular interest is the effect of polymer additives on the linear stability of two-dimensional viscous flow past a confined cylinder and our investigation involves both direct numerical sim...

A finite volume method based on a velocity-only formulation is used to solve the flow field around a confined circular cylinder in a channel in order to investigate lateral wall proximity effects on stability, Strouhal number, hydrodynamic forces and wake structure behind the cylinder for a wide range of blockage ratios (0.10.9) and Reynolds number...

A novel implicit cell-vertex finite volume method is presented for the solution of both the Navier-Stokes equations and the governing equations for certain viscoelastic fluids. The key idea is the elimination of the pressure term from the momentum equation by multiplying the momentum equation with the unit normal vector to a control volume boundary...

A method which uses only the velocity components as primitive variables is described for solution of the incompressible unsteady Navier–Stokes equations. The method involves the multiplication of the primitive variable-based Navier–Stokes equations with the unit normal vector of finite volume elements and the integration of the resulting equations...

A novel implicit cell-vertex finite volume method is described for the solution of the Navier–Stokes equations at high Reynolds numbers. The key idea is the elimination of the pressure term from the momentum equation by multiplying the momentum equation with the unit normal vector to a control volume boundary and integrating thereafter around this...

A novel finite volume method, described in Part I of this paper (Sahin and Owens, Int. J. Numer. Meth. Fluids 2003; 42:57–77), is applied in the linear stability analysis of a lid-driven cavity flow in a square enclosure. A combination of Arnoldi's method and extrapolation to zero mesh size allows us to determine the first critical Reynolds number...

A method based on an integral equation formulation is described for solution of the full potential equation in terms of the velocity field. In addition to the conventional distribution of singularities over the boundaries of field, a field source distribution is added in the flow region in order to represent the non-linear compressibility effect. T...

The dynamic stall characteristics of conventional airfoils used in helicopter blades, and airfoils whose shapes change dynamically with time are numerically studied. Two-dimensional Navier-Stokes equations in integral form are solved on a body-fitted grid that deforms as the airfoil changes its shape, and rotates with the airfoil in pitch. The sche...