Large eddy simulation of turbulent flow and mass transfer in far-field of swirl diffusers

Tavakoli, Ehsan; Hosseini, Reza

doi:10.1016/j.enbuild.2012.12.029

Cited by 16 publications

(9 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The higher velocities observed in VD case are due to the multi-jet configuration (Figure 4 c) resulting from impellers imprint, which seems persistent since the jets do not merge over the observation distance Z= 80 mm. The vortex jet is here radial contrary to the numerical predictions in [20], where the simulated vortex jet would be vertical for impellers angle of 45°. Furthermore, the jet rotation seems to be stopped by the Coanda effect.…”

Section: Accepted Manuscriptcontrasting

confidence: 61%

“…The accuracy in flow rate measurement is ±3% of the reading. hence, according to the numerical prediction of [20], the jet should be vertical.…”

Section: Accepted Manuscriptmentioning

confidence: 98%

“…The experimental studies in references [11,12] were cited or were used as a reference data in a number of numerical studies [18][19][20] dealing with CFD simulation of jets from ceiling vortex diffusers. The most recent numerical study [20] focuses on the effect of the angle between the impellers and the vertical axis, on the jet behavior and on the resulting air quality in the room (qualified by the predicted total age of the air [21,22]). The numerical results…”

Section: Accepted Manuscriptmentioning

confidence: 99%

See 2 more Smart Citations

Experimental analysis of mixing ventilation efficiency using a vortex diffuser: Comparison to a lobed multicone diffuser

Meslem

Bragança

Sodjavi

2018

Science and Technology for the Built Environment

View full text Add to dashboard Cite

In a recent work, an innovative multi-cone diffuser integrating lobed inserts as vortices promoters was proposed, and was compared to its counterpart without lobed inserts. The former offers better mixing of the jet with the ambient air, and significantly improves thermal comfort. In this study, the innovative diffuser is compared to a vortex diffuser under the same experimental conditions. The vortex diffuser is described in the scientific and technical A c c e p t e d M a n u s c r i p t literature as the best diffuser in terms of mixing efficiency due to the swirling effect, being thereby a reference for the innovative lobed diffuser. The results demonstrate that the vortex diffuser does not produce the expected swirling effect. The rotation of the jet is prevented by the immediate attachment of the flow to the ceiling due to the Coanda effect. The jet behaves as a radial ceiling-attached flow having a poor mixing performance. It is believed that such a diffuser would be efficient when mounted on a long duct far away from the ceiling. Hence, it will be better suited for high ceilings, such as in industrial or commercial spaces. In this case, the proposed lobed diffuser becomes an appropriate and efficient mixing ventilation solution for rooms having low ceiling heights. KEYWORDS Mixing ventilation, lobed diffuser, vortex diffuser, cold jet, PIV measurements, thermal comfort PRACTICAL IMPLICATIONS Flow pattern and thermal comfort are analyzed in a room under mixing ventilation. Vortex (VD) and multi-cone lobed (LD) diffusers are compared in a cooling mode. The jet rotation vanishes near the VD exit due to the Coanda effect. It results in poor mixing performance for VD compare to LD. LD is best in terms of thermal comfort, pressure loss and noise generation.

show abstract

Section: Accepted Manuscriptcontrasting

confidence: 61%

“…The accuracy in flow rate measurement is ±3% of the reading. hence, according to the numerical prediction of [20], the jet should be vertical.…”

Section: Accepted Manuscriptmentioning

confidence: 98%

Section: Accepted Manuscriptmentioning

confidence: 99%

See 1 more Smart Citation

Experimental analysis of mixing ventilation efficiency using a vortex diffuser: Comparison to a lobed multicone diffuser

Meslem

Bragança

Sodjavi

2018

Science and Technology for the Built Environment

View full text Add to dashboard Cite

show abstract

“…Drangan and Stanciu [19] used the k-ε model to observe a new super circulation technique to reduce drag and improve lift in aerospace applications. Tavakoli and Hosseini [20] investigated the relation between the Swirl number and the flow pattern using different angles in an axial vaned swirler used for ventilation applications. Although these and more advanced techniques such as LES [21,22] have been used for the study of the Coanda effect, the computational results have not shown the transient nature of the process.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

Valera‐Medina

Baej

2016

Flow Turbulence Combust

View full text Add to dashboard Cite

Swirl stabilized flows are the most widely deployed technology used to stabilize gas turbine combustion systems. However, there are some coherent structures that appear in these flows close to the nozzle whose occurrence and stability are still poorly understood during transition. The external recirculation zone and the Precessing Vortex Core to/from the Coanda effect are some of them. Thus, in this paper the transition of an Open Jet FlowMedium Swirl flow pattern to/from a Coanda jet flow is studied using various geometries at a fixed Swirl number. Phase Locked Stereo Particle Image Velocimetry and High Speed Photography experiments were conducted to determine fundamental characteristics of the phenomenon. It was observed that the coherent structures in the field experience a complete annihilation during transition, with no dependency between the structures formed in each of the flow states. Moreover, transition occurs at a particular normalized step size whilst some acoustic shifts in the frequencies of the system were noticed, a phenomenon related to the strength of the vortical structures and vortices convection. It is concluded that a transient, precessing, Coanda Vortex Breakdown is formed, changing flow dynamics. The structure progresses to a less coherent Trapped Vortex between the two states. During the phenomenon there are different interactions between structures such as the Central Recirculation Zone, the High Momentum Flow Region and the Precessing Vortex Core that were also documented.

show abstract

“…It is almost half a century since this problem has been tackled with a family of numerical schemes called the projection methods pioneered by Temam and Chorin . These methods have now become the principle numerical tools for many numerical simulations on both staggered and collocated grids covering a wide range of flows including highly variable density , multiphase granular flows , free‐surface flows , and many others.…”

Section: Introductionmentioning

confidence: 99%

An accurate pressure–velocity decoupling technique for semi‐implicit rotational projection methods

Tavakoli

2016

Numerical Methods in Fluids

Self Cite

View full text Add to dashboard Cite

Summary In this paper, an accurate semi‐implicit rotational projection method is introduced to solve the Navier–Stokes equations for incompressible flow simulations. The accuracy of the fractional step procedure is investigated for the standard finite‐difference method, and the discrete forms are presented with arbitrary orders or accuracy. In contrast to the previous semi‐implicit projection methods, herein, an alternative way is proposed to decouple pressure from the momentum equation by employing the principle form of the pressure Poisson equation. This equation is based on the divergence of the convective terms and incorporates the actual pressure in the simulations. As a result, the accuracy of the method is not affected by the common choice of the pseudo‐pressure in the previous methods. Also, the velocity correction step is redefined, and boundary conditions are introduced accordingly. Several numerical tests are conducted to assess the robustness of the method for second and fourth orders of accuracy. The results are compared with the solutions obtained from a typical high‐resolution fully explicit method and available benchmark reports. Herein, the numerical tests are consisting of simulations for the Taylor–Green vortex, lid‐driven square cavity, and vortex–wall interaction. It is shown that the present method can preserve the order of accuracy for both velocity and pressure fields in second‐order and high‐order simulations. Furthermore, a very good agreement is observed between the results of the present method and benchmark simulations. Copyright © 2016 John Wiley & Sons, Ltd.

show abstract

Large eddy simulation of turbulent flow and mass transfer in far-field of swirl diffusers

Cited by 16 publications

References 18 publications

Experimental analysis of mixing ventilation efficiency using a vortex diffuser: Comparison to a lobed multicone diffuser

Experimental analysis of mixing ventilation efficiency using a vortex diffuser: Comparison to a lobed multicone diffuser

Hydrodynamics During the Transient Evolution of Open Jet Flows from/to Wall Attached Jets

An accurate pressure–velocity decoupling technique for semi‐implicit rotational projection methods

Contact Info

Product

Resources

About