scholarly journals Numerical Laser Energy Deposition on Supersonic Cavity Flow and Sensor Placement Strategies to Control the Flow

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Ibrahim Yilmaz ◽  
Selin Aradag
Keyword(s):  
Energy Deposition ◽  
Laser Energy ◽  
Leading Edge ◽  
Cavity Flow ◽  
Time Flow ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Proper Orthogonal ◽  
The Impact ◽  
Supersonic Cavity

In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to thex-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications.

Contributions of Tip Leakage and Inlet Diffusion on Inducer Backflow

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
D. Tate Fanning ◽  
Steven E. Gorrell ◽  
Daniel Maynes ◽  
Kerry Oliphant
Keyword(s):  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Low Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow Recirculation ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Inducers are used as a first stage in pumps to minimize cavitation and allow the pump to operate at lower inlet head conditions. Inlet flow recirculation or backflow in the inducer occurs at low flow conditions and can lead to instabilities and cavitation-induced head breakdown. Backflow of an inducer with a tip clearance (TC) of τ = 0.32% and with no tip clearance (NTC) is examined with a series of computational fluid dynamics simulations. Removing the TC eliminates tip leakage flow; however, backflow is still observed. In fact, the NTC case showed a 37% increase in the length of the upstream backflow penetration. Tip leakage flow does instigate a smaller secondary leading edge tip vortex that is separate from the much larger backflow structure. A comprehensive analysis of these simulations suggests that blade inlet diffusion, not tip leakage flow, is the fundamental mechanism leading to the formation of backflow.

scholarly journals A Comparison of Experimental and Computational Heat Transfer Results for a Leading Edge Impingement System

2018 ◽  
Vol 3 (4) ◽  
pp. 23
Author(s):  
Robert Pearce ◽  
Peter Ireland ◽  
Ed Dane ◽  
Janendra Telisinghe
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
High Heat ◽  
Navier Stokes ◽  
Spatially Resolved ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Leading edge impingement systems are increasingly being used for high pressure turbine blades in gas turbine engines, in regions where very high heat loads are encountered. The flow structure in such systems can be very complex and high resolution experimental data is required for engine-realistic systems to enable code validation and optimal design. This paper presents spatially resolved heat transfer distributions for an engine-realistic impingement system for multiple different hole geometries, with jet Reynolds numbers in the range of 13,000–22,000. Following this, Reynolds-averaged Navier-Stokes computational fluid dynamics simulations are compared to the experimental data. The experimental results show variation in heat transfer distributions for different geometries, however average levels are primarily dependent on jet Reynolds number. The computational simulations match the shape of the distributions well however with a consistent over-prediction of around 10% in heat transfer levels.

Optimal Minimum Airflow for Air Circulation of Single-Duct VAV Terminal Boxes

2008 ◽  
Author(s):  
Young-Hum Cho ◽  
Mingsheng Liu
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Thermal Discomfort ◽  
Variable Air Volume ◽  
Air Handling Unit ◽  
Optimal Value ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Air Circulation ◽  
The Impact

Thermal comfort in an area is directly controlled by terminal boxes in variable air volume (VAV) air-handling unit (AHU) systems. The terminal box either modulates airflow or adjusts the discharge air temperature. Reduced air circulation will cause thermal discomfort in a conditioned space if the airflow and discharge air temperature are not suitable. The objective of this study is to identify an optimal value for airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature is analyzed, and the impact of room airflow and discharge air temperature on thermal stratification is verified through CFD (Computational Fluid Dynamics) simulations.

The Effect of Blade Leading Edge Platform Shape on Upstream Disk Cavity to Mainstream Flow Interaction of a High-Pressure Turbine Stage

2007 ◽  
Author(s):  
Remo Marini ◽  
Sami Girgis
Keyword(s):  
Leading Edge ◽  
Cavity Flow ◽  
Flow Interaction ◽  
Passage Vortex ◽  
Mainstream Flow ◽  
Transient Simulations ◽  
The Impact ◽  
Stage Efficiency ◽  
Engine Condition ◽  
Blade Leading Edge

This paper presents a CFD study of a transonic highpressure 1-stage turbine that includes the blade upstream disk cavity. The emphasis of the analysis was to understand and quantify the impact of the blade leading edge platform shape on the flow interaction between the upstream disk cavity flow and the gaspath mainstream flow. Two blade platform shapes were analyzed: a recessed and a raised leading edge shape. The results presented include steadystate and transient simulations in order to describe the flow interaction and quantify the impact on stage efficiency. A sensitivity analysis on the amount of cavity flow was performed to investigate the impact on secondary losses (interpreted by entropy generation) and stage efficiency. It was found that the blade leading edge platform shape and cavity flow amount affected the blade hub passage vortex structure and location. At the nominal engine condition, the raised leading edge platform shape showed an improvement in stage efficiency. It also showed a reduced sensitivity of stage efficiency due to cavity flow amount.

scholarly journals Computational fluid dynamics simulations of the impact of a water spray on a fire-induced smoke layer inside a hood

2018 ◽  
Vol 36 (5) ◽  
pp. 380-405 ◽  
Author(s):  
Zhi Tang ◽  
Zheng Fang ◽  
Jiayun Sun ◽  
Tarek Beji ◽  
Bart Merci
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Sensitivity Study ◽  
Spray Angle ◽  
Water Spray ◽  
Smoke Layer ◽  
Computational Fluid Dynamics Simulations ◽  
Simulation Results ◽  
Dynamics Simulations ◽  
The Impact

This article presents computational fluid dynamics results of the impact of a water spray on the fire smoke layer inside a hood. The models and the settings of parameters are discussed. Three experiments are performed by means of computational fluid dynamics simulations, and the comparisons show good agreement between measured data and predicted results. The simulation results provide insight into the temperature and flow fields for the configuration at hand, revealing an entrainment effect. The influence of the water spray characteristics on the downward smoke displacement due to drag and cooling is explained. Furthermore, an extensive sensitivity study of the simulation results to input parameters and mesh size is performed. The inner spray angle (related to vertical water flux) and droplet size are shown to be key parameters when simulating downward smoke displacement caused by a spray.

scholarly journals Computational investigation of cicada aerodynamics in forward flight

2015 ◽  
Vol 12 (102) ◽  
pp. 20141116 ◽  
Author(s):  
Hui Wan ◽  
Haibo Dong ◽  
Kuo Gai
Keyword(s):  
Vortex Ring ◽  
High Speed ◽  
Three Dimensional ◽  
Leading Edge ◽  
Ring Structure ◽  
Forward Flight ◽  
Edge Vortex ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations ◽  
Wing Tip

Free forward flight of cicadas is investigated through high-speed photogrammetry, three-dimensional surface reconstruction and computational fluid dynamics simulations. We report two new vortices generated by the cicada's wide body. One is the thorax-generated vortex, which helps the downwash flow, indicating a new phenomenon of lift enhancement. Another is the cicada posterior body vortex, which entangles with the vortex ring composed of wing tip, trailing edge and wing root vortices. Some other vortex features include: independently developed left- and right-hand side leading edge vortex (LEV), dual-core LEV structure at the mid-wing region and near-wake two-vortex-ring structure. In the cicada forward flight, approximately 79% of the total lift is generated during the downstroke. Cicada wings experience drag in the downstroke, and generate thrust during the upstroke. Energetics study shows that the cicada in free forward flight consumes much more power in the downstroke than in the upstroke, to provide enough lift to support the weight and to overcome drag to move forward.

scholarly journals Influence of the Slag Density on the Splashing Process in a Steelmaking Converter

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Miguel A. Barron ◽  
Dulce Y. Medina ◽  
Isaias Hilerio ◽  
Gabriel Plascencia
Keyword(s):  
Fluid Dynamics ◽  
Volume Fraction ◽  
Two Dimensional ◽  
Average Volume ◽  
Qualitative Comparison ◽  
Slag Splashing ◽  
Computational Fluid Dynamics Simulations ◽  
Oxygen Steelmaking ◽  
Dynamics Simulations ◽  
The Impact

The way in which slag density influences the slag splashing phenomenon in an oxygen steelmaking converter is numerically analyzed in this work. Several values of the density of the slag are considered, and their effect on the global mass balance and slag average volume fraction on the sidewalls of the converter is studied using isothermal, two-dimensional transient computational fluid dynamics simulations. Diameter of the slag drops is determined from the slag density and the impact velocity of the nitrogen jet. Besides, the effect of the nitrogen jet Mach number on the slag splashing is simulated and discussed. A qualitative comparison between the computer simulations and results from the literature is made.

Optimization for vertical stabilizers on flutter stability of streamlined box girders with mountainous environment

2019 ◽  
Vol 23 (2) ◽  
pp. 205-218 ◽  
Author(s):  
Junjie Guo ◽  
Haojun Tang ◽  
Yongle Li ◽  
Lianhuo Wu ◽  
Zewen Wang
Keyword(s):  
Leading Edge ◽  
Mountainous Areas ◽  
Box Girders ◽  
Box Girder ◽  
Long Span Bridges ◽  
Long Span ◽  
Participation Level ◽  
Computational Fluid Dynamics Simulations ◽  
Strong Winds ◽  
Dynamics Simulations

Wind environment in mountainous areas is very different from that in coastal and plain areas. Strong winds always show large angles of attack, affecting the flutter stability of long-span bridges which is one of the most important design factors. The central vertical stabilizer has been demonstrated to be an effective aerodynamic measure to improve the flutter stability, and this article optimizes the stabilizer to improve its applicability in mountainous areas. Computational fluid dynamics simulations are first performed to analyze the effects of stabilizers with different positions and forms on the flutter stability of an ideal box girder, and the aerodynamic mechanism is discussed based on the static and the dynamic flow fields, respectively. Wind tunnel tests are then carried out to test the critical flutter wind speed of a real box girder equipped with different stabilizers, and the change in its flutter stability is further analyzed. The results show that the vertical stabilizer with appropriate positions and heights can improve the participation level of structural heaving vibration, and thereby increases the flutter stability. At large angles of attack, the big vortex on the leading edge which may drive the bridge to flutter instability is gradually weakened with the increase in stabilizer’s height. Compared with a single stabilizer, double vertical stabilizers, in the midst of which exists a negative pressure region, could achieve better effects.

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