scholarly journals Flow and windage due to bolts on a rotating disc

2016 ◽  
Vol 231 (15) ◽  
pp. 2925-2941
Author(s):  
Sulfickerali Noor Mohamed ◽  
John Chew ◽  
Nick Hills
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Time Dependent ◽  
Navier Stokes ◽  
Rotating Disc ◽  
Rotating Machine ◽  
Flow Features ◽  
Rotor Surface ◽  
Dynamics Simulations ◽  
Cooling Air

The cooling air in a rotating machine is subject to windage as it passes over the rotor surface, particularly for cases where nonaxisymmetric features such as boltheads are encountered. The ability to accurately predict windage can help reduce the quantity of cooling air required, resulting in increased efficiency. Previous work has shown that the steady computational fluid dynamics solutions can give reasonable predictions for the effects of bolts on disc moment for a rotor–stator cavity with throughflow but flow velocities and disc temperature are not well predicted. Large fluctuations in velocities have been observed experimentally in some cases. Time-dependent computational fluid dynamics simulations reported here bring to light the unsteady nature of the flow. Unsteady Reynolds-averaged Navier–Stokes calculations for 120° and 360° models of the rotor–stator cavity with 9 and 18 bolts were performed in order to better understand the flow physics. Although the rotor–stator cavity with bolts is geometrically steady in the rotating frame of reference, it was found that the bolts generate unsteadiness which creates time-dependent rotating flow features within the cavity. At low throughflow conditions, the unsteady flow significantly increases the average disc temperature.

scholarly journals Viscous Computational Fluid Dynamics as a Relevant Decision-Making Tool for Mast-Sail Aerodynamics

2005 ◽  
Vol 42 (01) ◽  
pp. 1-10
Author(s):  
V. G. Chapin ◽  
S. Jamme ◽  
P. Chassaing
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Transition Process ◽  
Separated Flows ◽  
Navier Stokes ◽  
Recirculation Bubble ◽  
Qualitative And Quantitative ◽  
Turbulent Transition ◽  
Flow Features ◽  
Edge Separation

Viscous computational fluid dynamics based on Reynolds averaged Navier-Stokes (RANS) equations have been used to simulate flow around typical mast-sail geometries. It is shown how these advanced numerical methods are relevant to investigate the complexity of such strongly separated flows. Detailed numerical results have been obtained and compared to experimental ones. Comparative analysis has shown that RANS methods are able to capture the main flow features, such as mast-flow separation, recirculation bubble, bubble reattachment through a laminar-turbulent transition process, and trailing-edge separation. A second part has been devoted to the comparative behavior of these flow features through parameters variations to evaluate the qualitative and quantitative capabilities of RANS methods in mast-sail design optimization. The last part illustrates through two examples how RANS methods may be used to optimize the design of mast-sail geometries and evaluate their relative performances.

Investigation of pedestrian-level wind environment near two high-rise buildings in different arrangements

2019 ◽  
Vol 22 (12) ◽  
pp. 2620-2634
Author(s):  
Hemant Mittal ◽  
Ashutosh Sharma ◽  
Ajay Gairola
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Direction ◽  
Strong Wind ◽  
Wind Environment ◽  
High Rise ◽  
Flow Features ◽  
Staggered Arrangement ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

The presence of buildings that surround the wind environment adversely affects at the pedestrian level. The present study investigates the effect of different arrangement of two buildings on wind flow structure and modification of wind speed conditions at the pedestrian level. The investigation was carried out for parallel, tandem, and staggered arrangement of two buildings using computational fluid dynamics simulations. The wind tunnel experiments were conducted to validate the computational fluid dynamics results. The computational fluid dynamics simulations were performed using the standard [Formula: see text] model with LK modification and revised closure coefficients. Different flow features such as skew-symmetric vortex structure for parallel arrangement, reattachment of shear layer on the surfaces of the downstream building for tandem arrangement, and deviation of wake region behind the upstream building to leftward of the flow direction for staggered arrangement were observed. It was observed that the strong wind conditions were mostly affected by tandem and parallel location of the twin buildings. The results of numerical simulation obtained using the modified SKE model were found to be in good agreement with the experimental results.

scholarly journals Computational Fluid Dynamics Investigation on Multiple Injector Concepts at Different Swirl Ratios in a Heavy Duty Engine

2020 ◽  
Author(s):  
Gustav Nyrenstedt ◽  
Moez Ben Houidi ◽  
Rafig Babayev ◽  
Hong Im ◽  
Bengt Johansson
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Waste Heat ◽  
High Heat ◽  
Heat Losses ◽  
Navier Stokes ◽  
Load Case ◽  
Waste Heat Recovery System ◽  
Dynamics Simulations

Abstract Numerical studies investigated how multiple injectors can reduce the high heat losses associated with swirl, as a further attempt to enhance thermal efficiencies of high-pressure combustion engines. Computational fluid dynamics simulations employed the Reynolds-averaged Navier-Stokes approach for one, two- and three injector configurations. High and medium load conditions were simulated at different swirl ratios. In general, an increased swirl ratio reduced engine efficiency. However, for all swirl ratios, three injectors provided higher efficiency. Two injectors decreased the heat losses for all swirl ratios, and injection against the swirl with multiple injectors provided high efficiencies. In combination with a waste heat recovery system, the two-injector case delivered an efficiency increase of 2.2%-points for the medium load case. Three injectors delivered high efficiencies at all swirl ratios as an effect of a high flow rate and low heat losses. The multiple injector configurations evaluated in this study proved non-beneficial for the high load case. Spray-to-spray interactions lowered the combustion — and indicated efficiencies. However, the three injector case showed potential for delivering high indicated efficiency, from an increased flow rate, at high loads.

scholarly journals Aerodynamic shape optimization of guided missile based on wind tunnel testing and computational fluid dynamics simulation

2017 ◽  
Vol 21 (3) ◽  
pp. 1543-1554 ◽  
Author(s):  
Goran Ocokoljic ◽  
Bosko Rasuo ◽  
Aleksandar Bengin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Tunnel ◽  
Dynamics Simulation ◽  
Navier Stokes ◽  
Technical Institute ◽  
Aerodynamic Loads ◽  
Thrust Vector ◽  
Dynamics Simulations ◽  
The Military

This paper presents modification of the existing guided missile which was done by replacing the existing front part with the new five, while the rear part of the missile with rocket motor and missile thrust vector control system remains the same. The shape of all improved front parts is completely different from the original one. Modification was performed based on required aerodynamic coefficients for the existing guided missile. The preliminary aerodynamic configurations of the improved missile front parts were designed based on theoretical and computational fluid dynamics simulations. All aerodynamic configurations were tested in the T-35 wind tunnel at the Military Technical Institute in order to determine the final geometry of the new front parts. The 3-D Reynolds averaged Navier-Stokes numerical simulations were carried out to predict the aerodynamic loads of the missile based on the finite volume method. Experimental results of the axial force, normal force, and pitching moment coefficients are presented. The computational results of the aerodynamic loads of a guided missile model are also given, and agreed well with.

Drill Riser Fairing Hydrodynamic Assessment With 3-Dimensional Computational Fluid Dynamics Simulations

2018 ◽  
Author(s):  
Lawrence Lai
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Navier Stokes ◽  
End Effects ◽  
3 Dimensional ◽  
Drilling Operations ◽  
Axial Dimension ◽  
Dynamics Simulations ◽  
Maintenance Requirements ◽  
The Cost

Fairings have historically been known to achieve in-line drag coefficients (Cdx) of approximately 0.60 across the Reynolds number (Re) range of 100,000 to 1,000,000, typical for the offshore environment [1]. The recent development of helically grooved drill riser buoyancy was shown to achieve Cdx values of 0.65 for this Re range [2], presenting a strong alternative to fairing products especially considering the additional installation, storage and maintenance requirements of fairings. Therefore it is the purpose of this paper to investigate possible fairing designs capable of achieving even lower Cdx values where fairings can still be beneficial in further reducing drag loading. This paper proposes a non-parallel reduced chord horseshoe (RCH) fairing design and is analysed using computational fluid dynamics (CFD) in 3-d using the transient k-epsilon (Reynolds-averaged Navier-Stokes) turbulence model. The modelling approach is validated against tow tank test data of a previous teardrop-shaped (TD) fairing design which showed good agreement with published, peer-reviewed literature. It was found CFD simulations with axially continuous fairings provide artificially low Cdx values due to the absence of fairing end-effects and gaps between fairing sections. In essence, an infinitely long and uninterrupted fairing in the riser axial dimension is not realistic. Incorporation of this discontinuity sees a significant increase in Cdx compared to the axially continuous fairing configuration. Although this is the case, it was found Cdx of approximately 0.48 or lower is achievable for the entire offshore Re range for the discontinuous fairing configuration (assuming a chord/diameter ratio of 2.0). Larger chord/diameter ratios would provide lower Cdx at the cost of a longer chord length which may impact fairing installation efficiency. Longer axial lengths would also achieve lower Cdx but with the risk of flutter instability. This development in RCH fairing design sees a possible option for further fairing applicability to offshore drilling operations where lower drag is desirable beyond that offered by the helically grooved buoyancy.

New Approach of Gas–Liquid Computational Fluid Dynamics Simulations for the Study of Minimum Quantity Cooling With Airblast Plain-Jet Injectors

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Christophe Diakodimitris ◽  
Youssef R. Iskandar ◽  
Patrick Hendrick ◽  
Pierre Slangen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Single Phase ◽  
Continuous Phase ◽  
Navier Stokes ◽  
Two Phase ◽  
New Approach ◽  
Metal Machining ◽  
Dynamics Simulations ◽  
Liquid Flows

Due to the complexity of multiphase flows, they are often studied with numerical simulations. These simulations must be validated with experimental results. This paper introduces a new approach to initialize the continuous phase of gas–liquid flows generated by airblast nozzles for microlubrication applications with a recently modified commercial computational fluid dynamics (CFD) code FINE™/Open. Microlubrication is a technology used in metal machining where the coolant flow rate is lower than with conventional flood cooling. In this paper, single-phase gas and two-phase liquid–gas flows are studied. The continuous phase is simulated using Reynolds-averaged Navier–Stokes (RANS) equations coupled with a k–ε turbulence model and the dispersed phase is simulated using a Lagrangian method. To validate these simulations, particle image velocimetry (PIV) and particle dynamics analysis (PDA) measurements have been performed. This study illustrates the possibility of performing complex two-phase simulations with the help of single-phase studies to initialize the continuous phase of the flow (i.e., the gas). The single-phase flow also helps in estimating the magnitudes of the droplet velocities.

scholarly journals Aerodynamic analysis of uphill drafting in cycling

2021 ◽  
Vol 24 (1) ◽  
Author(s):  
T. van Druenen ◽  
B. Blocken
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Scientific Literature ◽  
Sensitivity Analyses ◽  
Air Resistance ◽  
Wind Tunnel Measurements ◽  
Aerodynamic Effect ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

AbstractSome teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

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