Jet impingement onto a tapered hole: Influence of jet velocity and hole wall velocities on heat transfer and skin friction

Shuja, S.Z.; Yilbaş, Bekir Sami; Khan, Shafique M.A.

doi:10.1002/fld.1895

Cited by 8 publications

(3 citation statements)

References 18 publications

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“…They indicated that the changes in the structure of striations over the thickness of the sheet being cut were closely related to aerodynamic features of the jet flows in the laser produced kerf. Jet impingement studies in relation to laser processing were carried out by Yilbas et al (2002Yilbas et al ( , 2003 and Shuja et al (2009). However, the flow situation is considered to be two dimensional and axisymmetric, which was the case for the laser drilling applications.…”

Section: Introductionmentioning

confidence: 99%

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Jet impingement onto a laser produced kerf

Melhem

Yilbaş²,

Shuja³

2011

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose -The purpose of this paper is to investigate the heat transfer rates from the kerf surfaces and skin friction at the kerf wall due to the jet impingement in relation to laser cutting process. Design/methodology/approach -Three-dimensional modeling for the flow and heat transfer analysis is considered. The numerical scheme using the control volume approach is introduced to solve the governing equations of flow and heat transfer. The k-w turbulence model is incorporated to account for the turbulence. Findings -It is found that the Nusselt number and the skin friction remains high in the region next to the kerf inlet and it decreases towards the kerf exit for all kerf thicknesses considered. The flow acceleration in the kerf also results in the second peak of the Nusselt number and the skin friction.Research limitations/implications -The melting at the kerf surface was omitted and the constant temperature boundary representing the melt surface is incorporated in the analysis. However, care was taken during the mesh generation to avoid grid dependent solutions. Practical implications -The findings and discussions provide the useful information on the practical laser cutting process, in particular, physical insight into the effect of the kerf thickness on the heat transfer and skin friction. Originality/value -No previous work has been carried out in three-dimensional space to predict the heat transfer and skin friction, which are important for practical laser cutting applications. Therefore, the work reported is original.

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Section: Introductionmentioning

confidence: 99%

“…In the present study, jet impingement onto a heated slot (kerf) in relation to laser cutting process is carried out. The flow field in the kerf is simulated using the practical assisting gas parameters (Shuja et al, 2009). The heat transfer rates form the kerf surface and the skin friction at the kerf wall are predicted.…”

Section: Introductionmentioning

confidence: 99%

Jet impingement onto a laser produced kerf

Melhem

Yilbaş²,

Shuja³

2011

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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“…The findings revealed that the deterioration of cut quality with the gas pressure and stand-off distance was closely related to the mass flow rate reduction in the cut section. Shuja et al (2009) and Yilbas et al (2003) investigated heat transfer from the circular hole due to jet impingement. Their findings revealed that the wall temperature of the hole influenced the mass flow rate through the hole and the Nusselt number.…”

mentioning

confidence: 99%

Flow into a hole in relation to laser drilling: influence of coating thickness

Shuja

Yilbaş

2014

International Journal of Numerical Methods for Heat &Amp; Fluid Flow

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Purpose – In laser drilling applications, hole wall remains almost the melting temperature of the substrate material and the thermodynamic pressure developed at high temperature molten surface vicinity influences the heat transfer rates and the skin friction at the surface of the hole wall. This effect becomes complicated for the holes drilled in coated substrates. In this case, melting temperatures of the coating and base materials are different, which in turn modifies the flow field in the hole due to jet impingement. Consequently, investigation of the heat transfer rates from the hole wall surfaces and the skin friction at the hole surface becomes essential. The paper aims to discuss these issues. Design/methodology/approach – Numerical solution for jet impingement onto a hole with high wall temperature is introduced. Heat transfer rates and skin friction from the hole wall is predicted. The numerical model is validated with the experimental data reported in the open literature. Findings – The Nusselt number attains high values across the coating thickness and it drops sharply at the interface between the coating and the base material in the hole. Since fluid temperature in the vicinity of the substrate surface is higher than that of the wall temperature, heat transfer occurs from the fluid to the substrate material while modifying the Nusselt number along the hole wall. This results in discontinuity in the Nusselt variation across the coating-base material interface. The Raighly line effect enhances the flow acceleration toward the hole exit while increasing the rate of fluid strain. Consequently, skin friction increases toward the hole exit. The influence of average jet velocity on the Nusselt number and the skin friction is significant. Research limitations/implications – The findings are very useful to analyze the flow field in the hole at different wall temperature. In the simulations hole diameter is fixed in line with the practical applications. However, it may be changed to examine the influence of hole diameter on the flow field and heat transfer. However, this extension be more toward academic study than the practical significance. Practical implications – The complete modeling of turbulent flow jet flow impinging onto a hole is introduced and boundary conditions are well defined for the numerical solutions. The method of handing the physical problem will be useful for those working in the area of heat transfer and fluid flow. In addition, the importance of heat transfer rates and skin friction at the hole wall is established, which will benefit the practical engineers and the academicians working in the specific area of laser machining. Social implications – The findings are useful for those working to improve the laser technology in the machining area. Originality/value – The work presented is original and never being published anywhere else. The findings are reported in detail such that academicians and engineers are expected to benefit from this original contribution.

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Thermal Analysis of Laser Drilling Process

Yilbaş

2012

Laser Drilling

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Jet impingement onto a tapered hole: Influence of jet velocity and hole wall velocities on heat transfer and skin friction

Cited by 8 publications

References 18 publications

Jet impingement onto a laser produced kerf

Jet impingement onto a laser produced kerf

Flow into a hole in relation to laser drilling: influence of coating thickness

Thermal Analysis of Laser Drilling Process

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