MIDDLE EUROPEAN SCIENTIFIC BULLETIN ISSN 2694-9970 119 Middle European Scientific Bulletin, VOLUME 18 Nov 2021 Comparison of Turbulence Models for the Problem of an Asymmetric Two- Dimensional Plane Diffuser Erkin Urinboevich Madaliev, Murodil Erkinjon Ugli Madaliev, Ikrom Isroiljonovich Mullaev, Mardon Akhmadjon Ugli Shoev, Abdulfatto Rahimjon Ugli Ibrokhimov Ferghana Polytechnic Institute, Ferghana, Uzbekistan ABSTRACT In this paper, the turbulent flow in an asymmetric two-dimensional diffuser is investigated. In many applications, it is important to know whether the boundary layer (laminar or turbulent by calculating the Reynolds number, which is the ratio of the inertia force to the viscous fluid flow force) will separate from the surface or inside a particular body. If this happens, it is also important to know exactly where the flow separation will occur. The separation can be internal or external. This is quite important in many tasks. KEYWORDS: Navier-Stokes equations, SIMPLE, RANS approach, control volume method. Introduction Currently, high-performance computers allow engineers to simulate turbulent flows in areas with complex geometry by numerically solving the equations of hydrodynamics, including the equations of momentum, continuity and energy using one of the existing methods of computational fluid dynamics CFD (Computational Fluid Dynamics). CFD codes are a powerful tool for researching practical problems and give satisfactory results. As a rule, CFD has become the basis for understanding the basics of flow processes, such as fluid flow, heat transfer, mass transfer, and has recently found application in medical fields [1]. Flow separation occurs when the boundary layer passes far enough away from the unfavorable pressure gradient, so that the velocity of the boundary layer relative to the object drops to almost zero [2,3]. The fluid flow breaks away from the surface of the object and as a result takes the form of vortices. The boundary layer closest to the wall or leading edge is flipped in the direction of flow. The point between the forward and reverse flow is called the separation point, where the shear stress is zero. Initially, the entire boundary layer thickens rapidly at the point of separation, and then is repelled from the surface by the reverse flow [4]. Sebechi et al. [5] accurately calculated the separation points in incompressible turbulent flows using four prediction methods, the Goldschmid, Stratford, Head and Chebechi-Smith method, and then confirmed them experimentally. Knob et al . [6] studied the dynamics of boundary layer separation using the PIV method and time-resolved biorthogonal decomposition in order to theoretically study the rapid structure of the separation region, its development and coherent structures, as well as the simple case of an unfavorable pressure gradient. Gustavsson [7] and Yan et al. [8] experimentally studied flow separation using a high- resolution PIV (Particle Image Velocimetry) system to study the rapid structure of the separation region, its development and the attachment of a turbulent flow. The results obtained were compared with conventional measurements using static pressure taps [8], a hot-wire anemometer and a Preston tube. Chandavari et al., [9] investigated the flow flow in a flat diffuser by changing the cone angle of the diffuser for axisymmetric expansion to delay separation. Thornblom et al. [10] experimentally