scholarly journals Parametric Output of Penetration Length in De-Laval Nozzle using Computational Fluid Dynamics

2020 ◽  
Vol 8 (6) ◽  
pp. 585-592
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laval Nozzle ◽  
Pressure Ratio ◽  
Research Work ◽  
Variable Pressure ◽  
Penetration Length ◽  
Rocket Nozzle ◽  
Half Angle ◽  
De Laval Nozzle

A Contour shaped rocket nozzle, commonly known as Bell nozzle, is a more efficient form of a De-Laval nozzle useful for operation at different altitudes resulting in variable pressure ratio across the nozzle. Here the penetration length during the flow is calculated in a De-Laval nozzle using Computational fluid dynamics (CFD). The TOP nozzle] by G.V.R. Rao is modeled and simulated using CFD analysis by varying the divergent half angle of the bell nozzle. The geometry of different divergent angle of the bell nozzle is modeled using MATLAB code. The modeled geometry and mesh of the nozzle is simulated in ANSYS-FLUENT software. The simulation shows the variation in different flow parameter at different divergent half angles. The analysis so far for the same is done in a conical shaped rocket nozzle at the cost of varying the divergent length for changing the divergent half angle of the nozzle. This project simulates bell nozzle with constant divergent length. The simulation model is verified and validated using experimental and computational data at an NPR (Nozzle pressure ratio) of 1000. As the Rao Nozzle is used currently in rocket, missile, and satellite control systems worldwide. This research work to show how the penetration length effect the Mass-Weighted average Mach number in a particular designed bell nozzle with different divergent half angle. Based on the results obtained, the discussion is done about the parameters and the conclusion is given

Effect of Cavities in Suddenly Expanded Flow at Supersonic Mach Number

CFD letters ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 57-71
Author(s):  
Atifatul Ismah Ismail
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Base Pressure ◽  
Sudden Expansion ◽  
Expansion Level ◽  
Computational Fluid Dynamics Cfd ◽  
Base Drag

The contribution from the base drag due to the sub-atmospheric pressure is significant. It can be more than two-thirds of the net drag. There is a need to increase the base pressure and hence decrease the base drag. This research examines the effect of Mach Number on base pressure. To accomplish this objective, it controls the efficacy in an enlarged duct computed by the numerical approach using Computational Fluid Dynamics (CFD) Analysis. This experiment was carried out by considering the expansion level and the aspect cavity ratio. The computational fluid dynamics method is used to model supersonic motion with the sudden expansion, and a convergent-divergent nozzle is used. The Mach number is 1.74 for the present study, and the area ratio is 2.56. The L/D ratio varied from 2, 4, 6, 8, and 10, and the simulated nozzle pressure ratio ranged from 3 to 11. The two-dimensional planar design used commercial software from ANSYS. The airflow from a Mach 1.74 convergent-divergent axi-symmetric nozzle expanded suddenly into circular ducts of diameters 17 and 24.5 mm with and without annular rectangular cavities. The diameter of the duct is taken D=17mm and D=24.5mm. The C-D nozzle was developed and modeled in the present study: K-ε standard wall function turbulence model was used with the commercial computational fluid dynamics (CFD) and validated. The result indicates that the base pressure is impacted by the expansion level, the enlarged duct size, and the passage’s area ratio.

Abstract WP121: An Evaluation of Hemodynamics Across Intracranial Steno-occlusive Lesions by Computational Fluid Dynamics

Stroke ◽  
2016 ◽  
Vol 47 (suppl_1) ◽  
Author(s):  
Florence SY Fan ◽  
Vincent HL Ip ◽  
Alexander YL Lau ◽  
Anne YY Chan ◽  
Lisa WC Au ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Gradient ◽  
Pressure Difference ◽  
Pressure Ratio ◽  
Velocity Ratio ◽  
Strongly Correlated ◽  
Hemodynamic Parameters ◽  
Moderate Correlation ◽  
Anterior Circulation

Introduction: Intracranial atherosclerotic steno-occlusive disease (ICAS) is a major cause of stroke worldwide and portends a high risk of recurrence. Computational fluid dynamics (CFD) is a novel technique developed to solve and analyze the dynamic effects of fluid flow. We aimed to analyse hemodynamics across ICAS using CFD on processed CTA images and explore the correlation between the degree of arterial stenosis and hemodynamic flow status. Methods: We recruited patients with symptomatic ICAS from Acute Stroke Unit, Prince of Wales Hospital. All patients received CTA and DSA as vascular workup. Using CFD analysis of processed CTA images, we first defined the hemodynamic parameters, including pressure difference, pressure ratio, pressure gradient, shear strain rate ratio (SSR), wall shear stress (WSS) ratio and velocity ratio, across the stenosed vessels, and then we correlated the severity of stenosis as defined by DSA, with these parameters. Results: Among the 53 recruited patients (mean age 62.9 years, 69.8% males), 45 (85%) had lesions in the anterior circulation. The severity of stenosis showed a weak-to-moderate correlation with pressure difference (rs=0.392, p=0.004), pressure ratio (rs=-0.429, p=0.001) and pressure gradient (rs=0.419, p=0.002). There was no significant correlation between the severity of stenosis with SSR ratio, WSS ratio and velocity ratio. Among patients with anterior circulation stroke or TIA, the severity of stenosis showed a weak to moderate correlation with pressure difference (rs=0.381, p=0.01), pressure ratio (rs=-0.426, p=0.004) and pressure gradient (rs=0.407, p=0.005). For patients with posterior circulation stroke or TIA, the severity of stenosis was strongly correlated with pressure difference (rs=0.714, p=0.047) and pressure ratio (rs=-0.714, p=0.047); and very strongly correlated with velocity ratio (rs=0.833, p=0.01). Conclusions: The severity of ICAS showed only weak-to-moderate correlation with hemodynamic parameters across the culprit lesion. Thus, risk stratification and treatment based solely on stenotic severity may be inadequate. Our findings may guide further research in estimating stroke risks and selection of high-risk patients who may benefit from adjunctive treatments.

scholarly journals A zonal approach for estimating pressure ratio at compressor extreme off-design conditions

2018 ◽  
Vol 20 (4) ◽  
pp. 393-404 ◽  
Author(s):  
José Galindo ◽  
Roberto Navarro ◽  
Luis Miguel García-Cuevas ◽  
Daniel Tarí ◽  
Hadi Tartoussi ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Speed ◽  
Internal Combustion Engines ◽  
Pressure Ratio ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
One Dimensional ◽  
Performance Map

Zero-dimensional/one-dimensional computational fluid dynamics codes are used to simulate the performance of complete internal combustion engines. In such codes, the operation of a turbocharger compressor is usually addressed employing its performance map. However, simulation of engine transients may drive the compressor to work at operating conditions outside the region provided by the manufacturer map. Therefore, a method is required to extrapolate the performance map to extended off-design conditions. This work examines several extrapolating methods at the different off-design regions, namely, low-pressure ratio zone, low-speed zone and high-speed zone. The accuracy of the methods is assessed with the aid of compressor extreme off-design measurements. In this way, the best method is selected for each region and the manufacturer map is used in design conditions, resulting in a zonal extrapolating approach aiming to preserve accuracy. The transitions between extrapolated zones are corrected, avoiding discontinuities and instabilities.

Computational Fluid Dynamics Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Yahya Dogu ◽  
Ahmet S. Bahar ◽  
Mustafa C. Sertçakan ◽  
Altuğ Pişkin ◽  
Ercan Arıcan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Ratio ◽  
Plate Thickness ◽  
Operating Conditions ◽  
Design Parameters ◽  
Backing Plate ◽  
Brush Seal ◽  
Front Plate ◽  
Brush Seals

Brush seals require custom design and tailoring due to their behavior driven by flow dynamic, which has many interacting design parameters, as well as their location in challenging regions of turbomachinery. Therefore, brush seal technology has not reached a conventional level across the board standard. However, brush seal geometry generally has a somewhat consistent form. Since this consistent form does exist, knowledge of the leakage performance of brush seals depending on specific geometric dimensions and operating conditions is critical and predictable information in the design phase. However, even though there are common facts for some geometric dimensions available to designers, open literature has inadequate quantified information about the effect of brush seal geometric dimensions on leakage. This paper presents a detailed computational fluid dynamics (CFD) investigation quantifying the leakage values for some geometric variables of common brush seal forms functioning in some operating conditions. Analyzed parameters are grouped as follows: axial dimensions, radial dimensions, and operating conditions. The axial dimensions and their ranges are front plate thickness (z1 = 0.040–0.150 in.), distance between front plate and bristle pack (z2 = 0.010–0.050 in.), bristle pack thickness (z3 = 0.020–0.100 in.), and backing plate thickness (z4 = 0.040–0.150 in.). The radial dimensions are backing plate fence height (r1 = 0.020–0.100 in.), front plate fence height (r2 = 0.060–0.400 in.), and bristle free height (r3 = 0.300–0.500 in.). The operating conditions are chosen as clearance (r0 = 0.000–0.020 in.), pressure ratio (Rp = 1.5–3.5), and rotor speed (n = 0–40 krpm). CFD analysis was carried out by employing compressible turbulent flow in 2D axisymmetric coordinate system. The bristle pack was treated as a porous medium for which flow resistance coefficients were calibrated by using literature based test data. Selected dimensional and operational parameters for a common brush seal form were investigated, and their effects on leakage performance were quantified. CFD results show that, in terms of leakage, the dominant geometric dimensions were found to be the bristle pack thickness and the backing plate fence height. It is also clear that physical clearance dominates leakage performance, when compared to the effects of other geometric dimensions. The effects of other parameters on brush seal leakage were also analyzed in a comparative manner.

Simulation of the Effect of Process Parameters on Particle Velocity in Cold Spray Using Laval Nozzle with Nine Holes

2011 ◽  
Vol 314-316 ◽  
pp. 78-81
Author(s):  
Chuan Shao Liu ◽  
Yao Hui Jin ◽  
Jian Xin Zheng
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Supersonic Flow ◽  
Flow Field ◽  
Particle Velocity ◽  
Laval Nozzle ◽  
Particle Diameter ◽  
Standoff Distance ◽  
Single Hole ◽  
Dynamics Method

Simulations of the supersonic flow field inside and outside of the Laval nozzle with single hole and nine holes were carried out based on the computational fluid dynamics method. The effects of different standoff distance and particle diameter on impact velocity of Cu particle spraying from single hole and nine holes were investigated firstly. The results show that the particle velocity obtained with the nine holes nozzle is higher than that of the single hole nozzle under the same standoff distance, and the smaller the standoff distance, the higher the particle velocity may be obtained with the nine holes, and the higher particle velocity may be obtained with smaller particle diameter for particles with diameters of 1 ~ 15 μm. Furthermore the effects of different spraying pressure and temperature on particle velocity of Cu particle spraying from the nine holes nozzle were also studied. And the simulations indicate that the higher the spraying pressure and temperature may make the particle spraying with greater velocity.

Investigation of an innovative non-free vortex aerodynamic procedure to design a single-stage transonic compressor

2017 ◽  
Vol 232 (11) ◽  
pp. 2132-2143 ◽  
Author(s):  
A Shahsavari ◽  
M Nili-Ahmadabadi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Design Method ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Meridional Plane ◽  
Transonic Compressor ◽  
Performance Map

This paper presents an innovative design method for a transonic compressor based on the radial equilibrium theory by means of increasing blade loading. Firstly, the rotor blade of a transonic compressor is redesigned based on the constant spanwise de-Haller number and diffusion. The design method leads to an unconventional increased axial velocity distribution in tip section, which originates from non-uniform enthalpy distribution assumption. A code is applied to extract the compressor meridional plane and blade-to-blade geometry containing rotor and stator in order to design the blade three-dimensional view. A structured grid is generated for the numerical domain of fluid. Finer grids are used for the regions near walls to capture the boundary layer effects and behavior. Reynolds-averaged Navier–Stokes equations are solved by finite volume method for rotating zones (rotor) and stationary zones (stator). The experimental data, available for the performance map of NASA Rotor67, is used to validate the results of the current simulations. Then, the capability of the design method is validated by computational fluid dynamics that is capable of predicting the performance map. The numerical results of the new geometry by representing 11% improvement in efficiency and 19% in total pressure ratio verify the new method advantages. The computational fluid dynamics results also show that the newly designed rotor blades due to a higher velocity in the tip section have a special capacity to increase the loading without any separation. The mass flow reduction is observed in the new geometry, which could be easily improved by changing stagger angle.

scholarly journals Functional assessment of cerebral artery stenosis: A pilot study based on computational fluid dynamics

2016 ◽  
Vol 37 (7) ◽  
pp. 2567-2576 ◽  
Author(s):  
Jia Liu ◽  
Zhengzheng Yan ◽  
Yuehua Pu ◽  
Wen-Shin Shiu ◽  
Jianhuang Wu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Invasive Procedure ◽  
Intracranial Stenosis ◽  
Parallel Computer ◽  
Invasive Technique ◽  
Non Invasive ◽  
Dynamics Method

The fractional pressure ratio is introduced to quantitatively assess the hemodynamic significance of severe intracranial stenosis. A computational fluid dynamics-based method is proposed to non-invasively compute the FPRCFD and compared against fractional pressure ratio measured by an invasive technique. Eleven patients with severe intracranial stenosis considered for endovascular intervention were recruited and an invasive procedure was performed to measure the distal and the aortic pressure ( Pd and Pa). The fractional pressure ratio was calculated as [Formula: see text]. The computed tomography angiography was used to reconstruct three-dimensional (3D) arteries for each patient. Cerebral hemodynamics was then computed for the arteries using a mathematical model governed by Navier–Stokes equations and with the outflow conditions imposed by a model of distal resistance and compliance. The non-invasive [Formula: see text], [Formula: see text], and FPRCFD were then obtained from the computational fluid dynamics calculation using a 16-core parallel computer. The invasive and non-invasive parameters were tested by statistical analysis. For this group of patients, the computational fluid dynamics method achieved comparable results with the invasive measurements. The fractional pressure ratio and FPRCFD are very close and highly correlated, but not linearly proportional, with the percentage of stenosis. The proposed computational fluid dynamics method can potentially be useful in assessing the functional alteration of cerebral stenosis.

A CFD (Computational Fluid Dynamics) Based Thermal Performance of Solar Air Heater With Rib-Roughened Channels

2016 ◽  
Author(s):  
Mumtaz Hussain Qureshi ◽  
M. Shakaib
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Heat Flux ◽  
Computational Fluid Dynamics ◽  
Research Work ◽  
Solar Air Heater ◽  
Transfer Coefficients ◽  
Turbulent Fluid Flow ◽  
Transfer Rates ◽  
Air Heater

Computational Fluid Dynamics (CFD) study is conducted to determine turbulent fluid flow and temperature profiles in rectangular ribbed channels of solar air heater. The results show significant effect of Reynolds number and ribs height and pitch on turbulence and heat transfer rates. When heat flux is defined at the bottom wall, the temperature values increase rapidly near the ribs due to stagnant zones. The heat transfer coefficients are lower at these locations. When heat flux is specified at the top wall, the variation in heat transfer coefficient is relatively smooth. From the research work, the channel containing ribs of 3mm and pitch 40mm are determined suitable due to higher heat transfer rates.

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