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.

Computational fluid dynamics analysis of the effect of throat diameter on the fluid flow and performance of ejector

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammadreza Salehi ◽  
Nader Pourmahmoud ◽  
Amir Hassanzadeh ◽  
S. Hoseinzadeh ◽  
P.S. Heyns
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Content Type ◽  
Standard Code ◽  
Computational Fluid Dynamics Analysis ◽  
Fluent Software ◽  
Computational Fluid Dynamics Cfd ◽  
Throat Diameter ◽  
And Performance

Purpose Using the computational fluid dynamics (CFD) technique, this paper aims to investigate the influence of key parameters such as throat diameter; the suction ratio on the flow field behaviors such as Mach number; pressure; and temperature. Design/methodology/approach To investigate the effect of throat diameter, it is simulated for 4, 6, 8 and 10 mm as throat diameters. The governing equations have been solved by standard code of Fluent Software together with a compressible 2 D symmetric and turbulence model with the standard k–ε model. First, the influence of the throat diameter is investigated by keeping the inlet mass flow constant. Findings The results show that a place of shock wave creation is changed by changing the throat diameter. The obtained results illustrate that the maximum amount of Mach number is dependent on the throat diameter. It is obtained from the results that for smaller throats higher Mach numbers can be obtained. Therefore, for mixing purposes smaller throats and for exhausting bigger throats seems to be appropriate. Originality/value The obtained numerical results are compared to the existing experimental ones which show good agreement.

Influence Mechanisms of Manufacture Variations on Supersonic/Transonic Blade Aerodynamic Performances

2020 ◽  
Author(s):  
Baojie Liu ◽  
Jiaxin Liu ◽  
Xianjun Yu ◽  
Dejun Meng ◽  
Wenbin Shi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Pressure ◽  
Statistical Analysis ◽  
Mach Number ◽  
Systematic Errors ◽  
Aerodynamic Performance ◽  
Aerodynamic Performances ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Abstract The results of previous studies have proved that manufacture variations can cause a noticeable influence on compressor aerodynamic performance. The main objective of this paper is to investigate the influence rules and mechanisms of manufacture variations on supersonic/transonic blades aerodynamic performance. The variations used in this study were measured from some newly manufactured high-pressure compressors. In the present study, several blade sections with different design Mach number conditions are selected for further statistical analysis of measured deviation data. Therefore, some systematic errors in the deviation data have been revealed. Based on these data, the computational fluid dynamics (CFD) method has been used to obtain the aerodynamic performances of a large number of the measured blade elements. And then, the analysis of the influence rules of manufacture variations on blade aerodynamic performance in different Mach number conditions has been carried out. The present results indicate that the effects of manufacture variations on blade aerodynamic performance in the lower Mach number (0.8) condition are much more significant comparing to that in the higher Mach number (0.9∼1.2) conditions. Based on this, influence mechanisms of manufacture variations on positive incidence range and negative incidence range have been analyzed. The differences of influence mechanisms in different Mach number conditions are the focus of research.

scholarly journals Aspects of aero-engine nacelle drag

2018 ◽  
Vol 233 (5) ◽  
pp. 1667-1682 ◽  
Author(s):  
Matthew Robinson ◽  
David G MacManus ◽  
Christopher Sheaf
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Wind Tunnel ◽  
Near Field ◽  
Pressure Ratio ◽  
Exhaust System ◽  
Extraction Methods ◽  
Field Method ◽  
Rate Of Change

To address the need for accurate nacelle drag estimation, an assessment has been made of different nacelle configurations used for drag evaluation. These include a sting mounted nacelle, a nacelle in free flow with an idealised, freestream pressure matched, efflux and a nacelle with a full exhaust system and representative nozzle pressure ratio. An aerodynamic analysis using numerical methods has been carried out on four nacelles to assess a near field drag extraction method using computational fluid dynamics. The nacelles were modelled at a range of aerodynamic conditions and three were compared against wind tunnel data. A comparison is made between the drag extraction methods used in the wind tunnel analysis and the chosen computational fluid dynamics approach which utilised the modified near-field method for evaluation of drag coefficients and trends with Mach number and mass flow. The effect of sting mounting is quantified and its influence on the drag measured by the wind tunnel methodology determined. This highlights notable differences in the rate of change of drag with free stream Mach number, and also the flow over the nacelle. A post exit stream tube was also found to create a large additional interference term acting on the nacelle. This term typically accounts for 50% of the modified nacelle drag and its inclusion increased the drag rise Mach number by around Δ M = 0.026 from [Formula: see text] to [Formula: see text] for the examples considered.

A 3D Computational Fluid Dynamics Analysis of the Wells Turbine

2002 ◽  
Author(s):  
John Daly ◽  
Ajit Thakker ◽  
Patrick Frawley ◽  
Elvis Sheik Bajeet
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Computational Model ◽  
Experimental Results ◽  
Dynamics Analysis ◽  
Cfd Model ◽  
Wells Turbine ◽  
Computational Fluid Dynamics Analysis ◽  
Computational Fluid Dynamics Cfd

This paper deals with the application of Computational Fluid Dynamics (CFD) to the turbulent analysis of the Wells Turbine. The objectives of this work were twofold; firstly to develop and benchmark the 3D CFD model and then to use this model to analyse the airflow through the turbine. The model was analysed as fully turbulent compressible flow using the Fluent™ CFD code. The computational model was first benchmarked against previously published experimental and CFD data for two similar turbines. The computational model accurately predicted the non-dimensional torque and non-dimensional pressure drop, while the efficiency predictions were lower than the experimental results. Predicted location of turbine stall also corresponded well with experimental results. Potential causes for differences between the computational and experimental results are suggested. The computational model was then analysed at both high and low tip Mach number settings and also with and without the tip gap, and these results were discussed.

scholarly journals ANALISA NILAI THRUST DAN TORQUE PROPELLER TIPE B-SERIES PADA KAPAL SELAM MIDGET 150M DENGAN VARIASI SKEW ANGLE DAN BLADE AREA RATIO (AE/AO) MENGGUNAKAN METODE CFD

Kapal ◽  
2016 ◽  
Vol 13 (3) ◽  
pp. 109
Author(s):  
Putra Bangkit Setyabudi ◽  
Deddy Chrismianto ◽  
Good Rindo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Area Ratio ◽  
Skew Angle ◽  
Blade Area ◽  
Angle Blade ◽  
Computational Fluid Dynamics Cfd

AbstrakKapal selam merupakan kapal yang mampu beroperasi dibawah air dengan mandiri, namun juga harus bergerak senyap dibawah air tanpa terdeteksi.  Maka dari itu salah satu kebutuhan paling penting dalam kapal selam adalah Baling-Baling atau Propeller. Baling-baling kapal selam membutuhkan beberapa kriteria khusus yaitu baling-baling kapal yang dapat memberikan gaya dorong yang besar dengan tingkat kebisingan yang rendah. Maka desain propeller harus memiliki nilai thrust yang besar, nilai tekanan yang rendah, dan aliran baling-baling yang halus. Penelitian ini menganalisa baling-baling kapal selam jenis B-7 Series dengan variasi Skew Angle (27.70, 29.70 dan 31.70) dan Blade Area Ratio (0.55, 0.59 dan 0.70) dengan penambahan Kort Nozzle C Tipe Shushkin Nozzle serta dengan tiga nilai RPM yaitu, 400 RPM, 450 RPM dan 500 RPM, sehingga didapatkan jenis baling – baling yang optimum untuk kapal selam midget type 150 m dengan menggunakan program Computational Fluid Dynamics (CFD). Dalam proses analisa menggunakan software berbasis CFD, kami mendapatkan hasil dari semua model baling – baling yaitu  bentuk aliran, nilai thrust dan nilai pressure yang berbeda sesuai dengan RPM yang diberikan. Dari kesembilan variasi model yang telah dibandingkan didapat model baling – baling yang optimum yaitu B – 7 Series pada Model 2 (27,70 & 0,59) putaran 400 RPM dengan nilai rata-rata tekanan 66,34 Pa, dan aliran turbulen dengan kecepatan rata - rata 15,56 m/s.Kata kunci : Kapal Selam, Propeller, Skew Angle, Blade Area Ratio (Ae/Ao), Kort Nozzle, dan CFD

Yaw Stability Analysis for UiTM's BWB Baseline-II UAV E-4

2013 ◽  
Vol 393 ◽  
pp. 323-328 ◽  
Author(s):  
Firdaus Mohamad ◽  
Wirachman Wisnoe ◽  
Rizal E.M. Nasir ◽  
Khairul Imran Sainan ◽  
Norhisyam Jenal
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stability Analysis ◽  
Mach Number ◽  
Deflection Angle ◽  
Rolling Moment ◽  
Yaw Stability ◽  
Directional Motion ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

This paper presents a study about yaw stability analysis for UiTMs Blended-Wing-Body (BWB) Baseline-II E-4. This aircraft is equipped with split drag flaps in order to perform directional motion. One of the split drag flaps will be deflected to generate yawing moment. This yawing moment is generated through the drag that is produced upon deflection of flaps. The study was carried out using Computational Fluid Dynamics (CFD) for various sideslip angles (β) and various flaps deflection angle (δT). The simulation was conducted at 0.1 Mach number (35 m/s) and results in terms of coefficient such yawing and rolling moment are tabulated in order to determine the stability of the aircraft. The result reveals that the aircraft is directionally unstable. This is as expected because the aircraft does not have any vertical tail configuration to provide the yawing moment. However, high deflection of split flaps can still generate adequate restoring moment for the aircraft.

scholarly journals Effects of Micro jets on the Flow Field of the Duct with Sudden Expansion

2019 ◽  
Vol 8 (9S2) ◽  
pp. 636-640 ◽  
Keyword(s):  
Mach Number ◽  
Flow Field ◽  
Pressure Distribution ◽  
Pressure Ratio ◽  
Wall Pressure ◽  
Base Pressure ◽  
Sudden Expansion ◽  
Orifice Diameter ◽  
Nozzle Pressure ◽  
Circle Diameter

This paper presents the results of an experimental investigation to study the effectiveness of the control jets to control base pressure in rapidly expanded circular tubes. Four tiny jets of 1 mm orifice diameter located at ninety degrees interval in cross shape along a pitch circle diameter of 1.3. The Mach number, the L/D ratio, and the area ratio of the study were 2.8, from 1 to 10, and 4.84, respectively. The nature of the flow field, the development of the flow in the duct, as well as the static wall pressure distribution in the duct was measured and discussed. The results indicate that the tiny jets can be used as an active dynamic controller for the base pressure. The wall pressure distribution is not adversely influenced by the small jets. From the present investigation, it is evident that for a given Mach number and nozzle pressure ratio one can identify the minimum duct L/D needed for the flow remained attached with the wall of the duct. The trend for the duct length L = 5D seems to show different results, due to the influence of back pressure and the peak pressure values are also less than that those were for higher L/D ratios, especially in respect of L/D = 5. Further, the flow field has smoothened in the duct, and wall pressure values with and without micro jets are identical. This trend continues until L/D = 4, then later for lower L/Ds like L/D = 3, the flow seems to be attached at higher NPRs. But for lower NPRs the flow is not attached

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