Numerical investigations of wall-bounded turbulence

Daud, Harbi A.; Li, Qinling; Bég, O. Anwar; Ghаni, Sаud

doi:10.1177/09544062jmes2524

Cited by 8 publications

(4 citation statements)

References 15 publications

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“…Hence, in this study, the RNG k-" model is chosen as the turbulent model for subsequent analyses, which is in perfect agreement with the findings of Dharavath et al [26] that the RNG k-" turbulence model performs better in predicting the base pressure. Furthermore, Daud et al [27] demonstrated from their numerical investigations of the wall-bounded flows that RNG turbulence model achieves the best accuracy when compared to other turbulence models.…”

Section: Validationmentioning

confidence: 96%

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Numerical investigation of the effects of base size on supersonic flow through a sudden duct enlargement

Lijo

Kim

Setoguchi

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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An abrupt increase in duct cross-section is often found in pressure-reducing devices, valves of internal-combustion engines, flow control devices in pipe systems of power plants, launch tubes of the ballistic ranges, thrust augmentation systems for cruise missiles, zero secondary flow ejectors, etc. The objective of this study is to revisit the classical base flow fields in a wall-bounded supersonic flow past a sudden expansion, to study and exploit their dependence on the size of the enlarged part -termed as the base size. Two-dimensional numerical simulations are performed for a nozzle flow, which is suddenly expanded in a larger rectangular channel. Five different turbulence models have been utilized in this study. Flow determination near the base is influenced by the proper selection of the turbulence model. The numerical solutions are compared with available experimental data and good agreement is achieved with renormalization group k-" turbulence model. This investigation is concerned with the determination of the base size, for which the jet characteristics and the base pressure become independent of the size of the enlarged part. For a given duct, base pressure tends to a minimum for a particular pressure ratio. In this study, the authors have been able to link the jet characteristics to the base size by both analytical and numerical methods. This has led to the conclusion that for a constant driving pressure, the base pressure asymptotically decreases when the base size is increased up to a critical value, and it becomes independent of the base size thereafter. It is believed that the results of this study can provide a better understanding of the wall-bounded supersonic flow past a sudden expansion. The relevance of the present observations in some of the engineering applications is also discussed.

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Section: Validationmentioning

confidence: 96%

“…Furthermore, Daud et al . [ 27 ] demonstrated from their numerical investigations of the wall-bounded flows that RNG turbulence model achieves the best accuracy when compared to other turbulence models.…”

Section: Validationmentioning

confidence: 99%

Numerical investigation of the effects of base size on supersonic flow through a sudden duct enlargement

Lijo

Kim

Setoguchi

2011

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…Numerical accuracy satisfactorily accomplished and amplified through refining the WBL mesh at the sub-layer area by present (y + ) value. The y + value is a specifically essential parameter to focus on the significance in simulations of CFD represents a great degree of accuracy y + ~12 as recommended by [18] when employing the RNG turbulence model with EWT. But, the value of y + <1 for LES as recommanded by [19].…”

Section: Geometry and Mesh For Film Holesmentioning

confidence: 99%

Film Cooling Holes Performance on A Flat Plate

Daud¹,

Mohammed²

2022

JMechE

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The present study aims to evaluate numerically the influence of film cooling holes configuration. Five models of holes configuration were studied to examine the effectiveness of a single film cooling hole (8 mm diameter). A cylindrical hole, square hole, rotated square, triangle hole and rotated triangle hole was employed to eject the coolant air with constant cross sectional area at 350 angle of injection. A 3-D finite-volume method was utilized to describe the turbulent flow over flat plate surface (as a model of a turbine blade surface). The mainstream domain (40d x10d x4d) had been represented in ANSYS FLUENT 16 with a standard turbulence model. So far, in term of effective cooling, the numerical results elucidate noticeable enhancement realized at BR=0.5 due to a reduction in plate surface temperature compared with BR =0.25 and 1 for cylindrical hole model. Moreover, the holes configuration performance demonstrate a better surface effectiveness about 1.6 % and 1.2 % for rotated triangle and square models respectively compared with the cylindrical holes model at BR=1. It was found that the numerical results had an excellent matching with related published results which show the solidity of ANSYS FLUENT code to predict the cooling efficiency with varying blowing ratio.

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“…The simulations show that the different coatings offer mixed benefits for TBC protection. These provide a useful compliment to alternative studies of gas turbine film cooling from a purely computational fluid dynamics view point or a purely stress analysis view point.…”

Section: Introductionmentioning

confidence: 99%

Computational fluid dynamic and thermal stress analysis of coatings for high‐temperature corrosion protection of aerospace gas turbine blades

Kadir

Bég

Gendy³

et al. 2019

Heat Trans. Asian Res.

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The current investigation presents detailed finite‐element simulations of coating stress analysis for a three‐dimensional, three‐layered model of a test sample representing a typical gas turbine component. Structural steel, titanium alloy, and silicon carbide are selected for main inner, middle, and outermost layers respectively. ANSYS is used to conduct three types of analysis—static structural, thermal stress analysis, and also computational fluid dynamic erosion (via ANSYS FLUENT). The specified geometry, which corresponds to corrosion test samples exactly, is discretized using a body‐sizing meshing approach, comprising mainly of tetrahedron cells. Refinements were concentrated at the connection points between the layers to shift the focus toward the static effects dissipated between them. A detailed grid independence study is conducted to confirm the accuracy of the selected mesh densities. The momentum and energy equations were solved, and the viscous heating option was applied to represent the improved thermal physics of heat transfer between the layers of the structures. A discrete phase model (DPM) in ANSYS FLUENT was used, which allows for the injection of continuous uniform air particles onto the model, thereby enabling an option for calculating the corrosion factor caused by hot air injection. Extensive visualization of results is provided. The simulations show that ceramic (silicon carbide) when combined with titanium clearly provide good thermal protection; however, the ceramic coating is susceptible to cracking and the titanium coating layer on its own achieves significant thermal resistance. Higher strains are computed for the two‐layer model than the single layer model (thermal case). However even with titanium only present as a coating the maximum equivalent elastic strain is still dangerously close to the lower edge. Only with the three‐layer combined ceramic and titanium coating model is the maximum equivalent strain pushed deeper towards the core central area. Here the desired effect of restricting high stresses to the strongest region of the gas turbine blade model is achieved, whereas in the other two models, lower strains are produced in the core central zones. Generally, the CFD analysis reveals that maximum erosion rates are confined to a local zone on the upper face of the three‐layer system which is in fact the sacrificial layer (ceramic coating). The titanium is not debonded or damaged which is essential for creating a buffer to the actual blade surface and mitigating penetrative corrosive effects. The present analysis may further be generalized to consider three‐dimensional blade geometries and corrosive chemical reaction effects encountered in gas turbine aero‐engines.

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Numerical investigations of wall-bounded turbulence

Cited by 8 publications

References 15 publications

Numerical investigation of the effects of base size on supersonic flow through a sudden duct enlargement

Numerical investigation of the effects of base size on supersonic flow through a sudden duct enlargement

Film Cooling Holes Performance on A Flat Plate

Computational fluid dynamic and thermal stress analysis of coatings for high‐temperature corrosion protection of aerospace gas turbine blades

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