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A turbulent kinetic theory due to Chung and a Green’s function method by Hong were employed to solve a reacting turbulent plane jet problem. An instantaneous mixing concept was used to simulate the steady state of turbulent plane jet with combustion. The probability density function description of the fluid elements in a turbulent reacting flow could properly explain the turbulent flame zone structure and the turbulent transport of heat, momentum and chemical species even under the infinitely fast reaction rate assumption. The calculated distributions of the various moments of the turbulent combustion field were found in good agreement with the available experimental data. The dynamic behaviour of combustion in the turbulent field could be better understood via the probability density function description of the present turbulent kinetic theory approach.

A numerical study is performed to investigate turbulent Couette flow and heat transfer characteristics in concentric annuli with a slightly heated inner cylinder moving in the flow direction. A two‐equation k‐ε turbulence model is employed to determine the turbulent viscosity and the turbulent kinetic energy. The turbulent heat flux is expressed by Boussinesq approximation in which the eddy diffusivity for heat is given as functions of the temperature variance t^2‐ and the dissipation rate of temperature fluctuations ε_t, together with k and ε. The governing boundary‐layer equations are discretized by means of control volume finite‐difference technique and numerically solved using a marching procedure. It is disclosed from the study that the streamwise movement of the inner core causes substantial reductions in the turbulent kinetic energy and the temperature variance, particularly near the inner wall region, resulting in the deterioration of the Nusselt number, and that an attenuation in heat transfer performance is induced by the velocity ratio of the moving inner cylinder to the fluid flow.

The construction industry is unique but with uncertainties. This is because of the operating environment. This intricacy gives rise to several construction risks and is compounded in developing countries’ turbulent times. If not managed, these risks enhanced in turbulent times could negatively impact the Nigerian construction projects’ cost, time, quality, and performance. Hence, this study investigated the perceived encumbrances facing construction risk management techniques and identified measures to promote sustainable-based construction risk management in turbulent times.

The researchers adopted a qualitative approach and achieved saturation with 28 participants. The participants were government policymakers, quantity surveyors in government ministries/agencies/departments, consultant engineers, consultant architects, consultant and contracting quantity surveyors, and construction contractors knowledgeable about construction risk management. The research employed a thematic analysis for the study’s data.

Findings identified turbulent times related to the industry and major techniques for managing construction project risks in the Nigerian construction industry. It revealed lax adoption and implementation of practices. Also, the study identified major encumbrances facing construction risk and proffered initiatives that would promote sustainable-based construction risk management in turbulent times.

This study investigates encumbrances and suggests measures to promote construction project risk management in turbulent times in Nigeria. Also, the study contributes to the literature’s paucity, uncovering perceived encumbrances and evolving organisations’ management styles to imbed sustainable-based risk management practices by qualitative research design method.

The purpose of the paper is to analyse the performances of closures and compressibility corrections classically used in turbulence models when applied to highly-compressible turbulent boundary layers (TBLs) over flat plates.

A direct numerical simulation (DNS) database of TBLs, covering a wide range of thermodynamic conditions, is presented and exploited to perform a priori analyses of classical and recent closures for turbulent models. The results are systematically compared to the “exact” terms computed from DNS.

The few compressibility corrections available in the literature are not found to capture DNS data much better than the uncorrected original models, especially at the highest Mach numbers. Turbulent mass and heat fluxes are shown not to follow the classical gradient diffusion model, which was shown instead to provide acceptable results for modelling the vibrational turbulent heat flux.

The main originality of the present paper resides in the DNS database on which the a priori tests are conducted. The database contains some high-enthalpy simulations at large Mach numbers, allowing to test the performances of the turbulence models in the presence of both chemical dissociation and vibrational relaxation processes.

This paper aims to provide improvements to the newest version of the k‐ ω turbulence model of Wilcox for convective heat transfer prediction in turbulent axisymmetric jets impinging onto a flat plate.

Improvements to the heat transfer prediction in the impingement zone are obtained using the stagnation flow parameter of Goldberg and the vortex stretching parameter of Wilcox. The third invariant of the strain rate tensor in the form of Shih et al. and the blending function of Menter are applied in order make negligible the influence of the impingement modifications in the benchmark flows for turbulence models. Further, it is demonstrated that for two‐dimensional jets impinging onto a flat plate the stagnation region Nusselt number predicted by the original k‐ ω model is in good agreement with direct numerical simulation (DNS) and experimental data. Also for two‐dimensional jets, the proposed modification is deactivated.

The proposed modification has been applied to improve the convective heat transfer predictions in the stagnation flow regions of axisymmetric jets impinging onto a flat plate with nozzle‐plate distances H/D = 2, 6, 10 and Reynolds numbers Re = 23,000 and 70,000. Comparison of the predicted and experimental mean and fluctuating velocity profiles is performed. The heat transfer rates along a flat plate are compared to experimental data. Significant improvements are obtained with respect to the original k‐ ω model.

The proposed modification is simple and can be added to the k‐ ω model without causing stability problems in the computations.

The purpose of this paper is to investigate the feasibility of solving turbulent flows based on smoothed finite element method (S-FEM). Then, the differences between S-FEM and finite element method (FEM) in dealing with turbulent flows are compared.

The stabilization scheme, the streamline-upwind/Petrov-Galerkin stabilization is coupled with stabilized pressure gradient projection in the fractional step framework. The Reynolds-averaged Navier-Stokes equations with standard k-epsilon model are selected to solve turbulent flows based on S-FEM and FEM. Standard wall functions are applied to predict boundary layer profiles.

This paper explores a completely new application of S-FEM on turbulent flows. The adopted stabilization scheme presents a good performance on stabilizing the flows, especially for very high Reynolds numbers flows. An advantage of S-FEM is found in applying wall functions comparing with FEM. The differences between S-FEM and FEM have been investigated.

The research in this work is limited to the two-dimensional incompressible turbulent flow.

The verification and validation of a new combination are conducted by several numerical examples. The new combination could be used to deal with more complicated turbulent flows.

The applications of the new combination to study basic and complex turbulent flow are also presented, which demonstrates its potential to solve more turbulent flows in nature and engineering.

This work carries out a great extension of S-FEM in simulations of fluid dynamics. The new combination is verified to be very effective in handling turbulent flows. The performances of S-FEM and FEM on turbulent flows were analyzed by several numerical examples. Superior results were found compared with existing results and experiments. Meanwhile, S-FEM has an advantage of accuracy in predicting boundary layer profile.

Because the local Re numbers, ratio of inertia to viscous forces, are not same at different regions of the enclosures, the present study aims to deal with the influences of using the turbulent/transition models on numerical results of the natural convection and flow field within a trapezoidal enclosure.

The three-dimensional (3D) trapezoidal enclosure with different inclined side walls of 75, 90 and 105 degrees are considered, where the side walls are heated and cooled at Ra = 1.5 × 10⁹ for all cases. The turbulent models of the k-ε-RNG, k- ω-shear-stress transport (SST) and the newly developed transition/turbulent model of Re_θ-γ-transition SST are utilized to analyze the fluid flow and heat transfer characteristics within the enclosure and compared their results with validated results.

Comprehensive comparisons have been carried out for all cases in terms of flow and temperature fields, as well as turbulent quantities, such as turbulent kinetic energy and turbulent viscosity ratio. Furthermore, the velocity and thermal boundary layers have been investigated, and the approximate transition regions for laminar, transitional and turbulent regimes have been determined. Finally, the heat transfer coefficient and skin friction coefficient values have been presented and compared in terms of different turbulent models and configurations. The results show that the transition/turbulence model has better prediction for the flow and heat fields than fully turbulent models, especially for local parameters for all abovementioned governing parameters.

The originality of this work is to analyze the 3D turbulent/transitional natural convection with different turbulence/transition models in a trapezoidal enclosure.

This paper aims to study turbulent dispersion of a passive plume emitting from a single elevated line source of different elevations in a plane channel flow by using direct numerical simulation (DNS).

The investigation was conducted in both physical and spectral spaces, which includes an analysis of statistical moments and pre-multiplied spectra of the velocity and concentration fields. The pre-multiplied power spectra of the velocity and concentration fields are compared to identify the transition of the plume development from the turbulent convective stage to the turbulent diffusive stage.

It is observed that due to the presence of wall shear, the mean plume drifts toward the wall for the near-wall source release case. It is also observed that streamwise development of the plume is sensitive to both the source elevation and the downstream distance from the source. For the line source placed near the center of the channel, the plume development is dominated by the bulk meandering effects. However, for the plume emitting from the near-wall line source, it hits the ground soon after its release and becomes dominated by the wall shear. As the downstream distance from the line source increases, the streamwise development of the plume released from the near-wall line source transitions from a turbulent convective stage to a turbulent diffusive stage.

This paper represents an original DNS study of turbulent mixing and dispersion of a passive plume emitting from a line source of different elevations in a wall-bounded flow. This paper proposes a practical method to identify the transition of the plume development from the turbulent convective to the turbulent diffusive stages.

A transport equation for the one‐point velocity probability density function (pdf) of turbulence is derived, modelled and solved. The new pdf equation is obtained by two modeling steps. In the first step, a dynamic equation for the fluid elements is proposed in terms of the fluctuating part of Navier‐Stokes equation. A transition probability density function (tpdf) is extracted from the modelled dynamic equation. Then the pdf equation of Fokker‐Planck type is obtained from the tpdf. In the second step, the Fokker‐Planck type pdf equation is modified by Lundgren’s formal pdf equation to ensure it can properly describe the turbulence intrinsic mechanism. With the new pdf equation, the turbulent plane Couette flow is solved by the direct finite difference method coupled with dimensionality reduction and QUICKER scheme. A simple boundary treatment is proposed such that the near‐wall solution is tractable and then no refined grid is required. The calculated mean velocity, friction coefficient, and turbulence structure are in good agreement with available experimental data. In the region departed from the center of flow field, the contours of isojoint pdf of V₁ and V₂ is very similar to that of experimental result of channel flow. These agreements show the validity of the new pdf model and the availability of the boundary treatment and QUICKER scheme for solving the turbulent plane Couette flow.

In this paper, we present a modified k‐ε model capable of addressing turbulent weld‐pool convection in the presence of a continuously evolving phase‐change interface during a gas tungsten arc welding (GTAW) process. The phase change aspects of the present problem are addressed using a modified enthalpy‐porosity technique. The k‐ε model is suitably modified to account for the morphology of the solid‐liquid interface. The two‐dimensional mathematical model is subsequently utilised to simulate a typical GTAW process with high power, where effects of turbulent transport can actually be realised. Finally, we compare the results from turbulence modelling with the corresponding results from a laminar model, keeping all processing parameters unaltered. The above comparison enables us to analyse the effects of turbulent transport during the arc welding process.