The Evaluation of k-ε and k-ω Turbulence Models in Modelling Flows and Performance of S-shaped Diffuser

Abstract

Diffusing S-shaped ducts are critical components in modern vehicle, primarily employed in directing the airflow to the engine. It links the air box and the engine in a very restricted place. The air flow through an S-duct is complex in nature, which perhaps includes boundary layer separation, secondary flow, and total pressure loss effects that influences the engine performance. In this work, the flow and performance of S-shaped duct was predicted and analysed using computational fluid dynamics. The main objective is to evaluate the performance of the realizable k-ε and k-ω SST models qualitatively and quantitatively in modelling flow of a highly bend duct where a high stress distorted flow may have developed in proximity the duct wall leading to stall. CFD computations were performed for the flow entering the diffuser at Reynolds number of 80,000 cases. The results obtained suggested that the k-ω SST model reasonably predicts the flow characteristics qualitatively and quantitatively. The realizable k-ε turbulence model however poorly captures the actual magnitudes of the calculated flow features. The growth of the stream-wise velocity profile was calculated at three stream-wise stations and point out a smooth down the interior profile of the divergent section. An extreme flow distortion and a shift of the region of flow with the highest velocity were developed toward the outer wall of the first bend of the diffuser. A significant pressure recovery potential with no flow separation arise over the diffuser tube range was predicted well by the simulations.

Comparison of Velocity Profiles in Stented Carotid Artery Bifurcation Between Computational Fluid Dynamics and Particle Image Velocimetry Measurements

“…This model also incorporates a transitional model with two additional transport equations, formulated locally for intermittency and the transition onset criterion, based on the momentum thickness Reynolds number. Featuring new correlations for transition, this model has been applied to a wide range of engineering problems, including turbomachinery [19], [21], [22], aircraft configurations, and wind turbines, and has shown promising results in cardiovascular flow applications [13]. The model is available in ANSYS CFX 19.0, and the numerical solution was achieved using an additive correction strategy alongside a coupled algebraic multigrid approach, achieving close to second-order accuracy, following the methodology established by [23].…”

A Review of Aerodynamics Influence on Various Car Model Geometry through CFD Techniques

“…Most journals studied in this review paper applied the 𝑘 − 𝜀 model and the 𝑘 − 𝜔 model due to its aerodynamic and airflow concepts. The 𝑘 − 𝜀 model is preferred when a study involves with free-shear layers and wake field whilst the 𝑘 − 𝜔 model is suitable to provides more accurate solutions in the near wall boundary regions [46][47][48][49].…”

Experimental and Numerical Analysis of a Motorcycle Air Intake System Aerodynamics and Performance

“…Due to the restriction of the space for storing the airbox under the rider seat, this generic airbox is equipped with a snorkel that in S-shaped geometry. The S-shape of the snorkel has a significant effect in flow dynamics and performance of the airbox system as a whole [25]. Figure 9(b) presents the skin friction coefficient, Cf contour of the s-duct at the inlet of the intake system at 90 cfm.…”

“…Patankar, Pratap [24] adopted a κ-ε type turbulence model to numerically predict the flow development in a curved pipe, recognising that the numerical prediction capability was not as satisfactory as for laminar flows. Lee, Allan [12] and Halim, Mohd [25] investigated a numerical analysis of the airflow inside an S-shaped tube using three different turbulence models, namely the κ-ε baseline κ-ω and κ-ω with Transport of Shear Stress (SST) models at the steady-state condition. The SST model has performed much better than the other two turbulence models.…”