A Method for Solving Problems of Irrotational Gas Flow by Means of High-Speed Digital Computers

1957 ◽  
Vol 24 (4) ◽  
pp. 497-500
Author(s):  
Toyoki Koga
Keyword(s):  
Flow Field ◽  
Analytical Methods ◽  
High Speed ◽  
Gas Flow ◽  
Fundamental Equation ◽  
Numerical Procedure ◽  
The State ◽  
Two Dimensional ◽  
Perfect Gas ◽  
Irrotational Flow

Abstract A numerical procedure is proposed for solution of certain problems in steady gas flow where subsonic, sonic, and supersonic regions appear simultaneously. The difficulties that occur in analytical methods for taking into account the differences of the type of the fundamental equation (elliptic, parabolic, hyperbolic) are avoided. Given a streamline and the state of the gas along that streamline, the co-ordinates of the neighboring streamline and the state of the gas along it can be computed. The procedure can be applied successively to cover a flow field. The method is described in detail for two-dimensional, steady, irrotational flow (without shocks) of a perfect gas, and an example is given.

A Stochastic Immersed Model of Breakup Characteristics in Dense Air Atomization Flow Field

2020 ◽  
Author(s):  
Tian Deng ◽  
Xingming Ren ◽  
Yaxuan Li
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Large Scale ◽  
Gas Flow ◽  
Liquid Core ◽  
Average Diameter ◽  
Simulation Method ◽  
Spray Angle ◽  
Random Structure ◽  
Momentum Ratio

Abstract For the low-speed liquid injected into the high-speed strong turbulent gas flow in the same direction, the atomization is a transient-intensive spray, and there are many factors affecting and controlling the atomization. In this paper, the distribution and characteristics of the liquid breakup in the air atomized flow field are analyzed. A stochastic immersed model to simulate the liquid core is developed, in which, the liquid core is regarded as an immersed porous medium with a random structure, and the probability of existence is used to simulate the position of the liquid core. The initial fragmentation mechanism of the air blast atomization is applied as the global variables of the stochastic process. Using the above stochastic immersed model, combined with the Large Eddy Simulation method, the numerical simulation of the downstream flow field of a coaxial jet air atomizing nozzle is carried out. Additional force is added to the momentum equation in the LES model. Instantaneous air velocity at the air-liquid interface is characterized by instantaneous liquid phase velocity at the same time. The size of the initial atomized droplet satisfies a probability distribution, and once the large droplets are formed, the Lagrangian method is used to track the droplets. The comparison between the simulation results and the experimental results shows that this stochastic immersed model can quickly capture the information of length and position of the liquid nucleus. When the gas-liquid momentum ratio M is 3∼10000, the liquid core length can be predicted more accurately. When M>10, the prediction result is much better than phenomenological model. This model is capable of capturing flow field structures such as recirculation zones and large-scale vortices. The results of initial spray angle from experiment expression give slightly better agreement with this model. Increasing the momentum ratio leads to decreasing of the initial spray angle. The particle size of the droplets near the nozzle can be accurately predicted, especially when the gas velocity is large (bigger than 60 m/s), and the average diameter prediction error of the droplets is less than 10%.

Preliminary Numerical Investigation of Effect of Interceptor on Ship Resistance

2011 ◽  
Vol 97-98 ◽  
pp. 1085-1090 ◽  
Author(s):  
Rui Deng ◽  
De Bo Huang ◽  
Guang Li Zhou ◽  
Hua Wei Sun
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Numerical Investigation ◽  
Satisfactory Agreement ◽  
High Speed ◽  
Three Dimensional ◽  
Numerical Results ◽  
Two Dimensional ◽  
Ship Resistance ◽  
The Right

In the present work, the CFD software FLUENT is used to calculate the ship resistance and simulate the flow field around it. Comparison of the numerical results with experimental data of the ship without interceptor shows basically satisfactory agreement in the case of high-speed. In order to get the right parameters of the interceptor for the ship, some two dimensional calculation is taken to study the influence of interceptor with different size. The simulation of the three dimensional vessel with interceptor is also included, and the effect is discussed.

Transient Surge Dynamics: A Shock Tube Theory and Experimental Comparison

2014 ◽  
Author(s):  
Paul Xiubao Huang ◽  
JianAn Yin
Keyword(s):  
Shock Tube ◽  
High Speed ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
The State ◽  
Transient Dynamics ◽  
Experimental Comparison ◽  
Time Duration ◽  
Dynamic Type

High-speed high-pressure ratio compressor surge is a transient breakdown in compression accompanied by an abrupt momentary reversal of gas flow. It commonly exists in dynamic type turbo compressors, particularly in the axial compressor of modern aero-engines. By Newton’s Laws of Motion, a force is needed to change the state of any motion. So what is the force that can cause such a dramatic motion as surge? What exactly triggers it, and how do we quantify the transient surge phenomenon? This paper attempts to answer these questions and discuss the transient dynamics of surge at its initial stage. It has generally been accepted that surge is precipitated by the onset of a rotating spike or stall, not only for low speed but for high-speed compressors too. The state of dynamic surge modeling today is best exemplified by the “Greitzer-Moore” model. However, it fails to incorporate the key elements of the transient nature of a surge inception: the extremely short time duration on millisecond scale and the shock wave presence observed experimentally. An indirect approach is taken in this paper to address the transient dynamics of stall and surge by using an analogy to the shock tube. The link is established based on observations that instant zero net through flow inside stalled cascade cell triggers stall/surge. The results from the analogy reveal that surge initiation simultaneously generates a pair of non-linear compression and expansion waves (CW & EW) and induced reverse fluid flow (IRFF). The dynamic forces for instant flow reversal are the pushing force of upstream propagating CW and the pulling force from downstream travelling EW. Surge Rules are deduced and then compared with experimental findings by previous researchers with good agreements. Moreover, the strength of the transient post-surge components, CW, EW and IRFF, can be estimated analytically or numerically by the shock tube theory from known pre-surge conditions and routes to surge.

Numerical Simulation Research of Air-Assisted Atomizer Internal Gas Flow Field Based on Fluent

2014 ◽  
Vol 599-601 ◽  
pp. 377-380
Author(s):  
Qiao Li ◽  
Ya Yu Huang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Total Pressure ◽  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Mutual Influence ◽  
Simulation Research ◽  
Simulation Calculation ◽  
Gas Flow Field

The numerical simulation calculation of air-assisted atomizer internal gas flow field is done, the distribution and changes of the nozzle inside flow field total pressure, velocity, and dynamic and static pressure are analyzed. The analysis shows that the total pressure loss is less; due to the effect of gas viscous, the high-speed air flow is formed vortex flow near the outlet nozzle and the mutual influence between the dynamic and static pressure. A new way is supported for optimizing the nozzle structure according to these studies.

Numerical Simulation of Flow Field within Mutational Section Pipe

2012 ◽  
Vol 192 ◽  
pp. 190-195
Author(s):  
Jian Hua Zhang ◽  
Kun Hu ◽  
Yi Fan Xu
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Pipe Flow ◽  
Gas Flow ◽  
Two Dimensional ◽  
One Dimensional ◽  
Compressed Gas ◽  
Interior Flow ◽  
Gas Flow Field

The section mutation of a pipe affects the interior flow field seriously. Numerical simulation of the two-dimensional steady gas flow field of two types of section mutation pipe was processed. By comparing it with equivalent section pipe’s interior flow field, the effects of section mutation of pipe on pressure distributing and velocity distributing were analyzed. The results are commendably consistent with the theories of one-dimensional adiabatic frictional pipe flow. Ensuring the section of the compressed gas pipe to be coherent and using the bell and spigot joint if necessary are presented.

Numerical Study on Flow Field Distribution Regularities in Wet Gas Desulfurization Tower Changing Inlet Gas/Liquid Feature Parameters

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Qingbo Deng ◽  
Jingyu Ran ◽  
Juntian Niu ◽  
Zhongqing Yang ◽  
Ge Pu ◽  
...  
Keyword(s):  
Flow Field ◽  
Field Distribution ◽  
Flue Gas ◽  
High Speed ◽  
Gas Flow ◽  
Negative Impact ◽  
Numerical Study ◽  
Negative Influence ◽  
Wet Gas ◽  
Integration Effect

Abstract In the wet gas desulphurization tower, the uneven distribution of flue gas will have a negative impact on the desulphurization process. The effect should be counterbalanced by increasing the amount of slurry spray, which will increase the operating costs. Adding deflectors will also bring negative effects and increase the expenses. In order to avoid the negative influence, this paper studied the flow field distribution regularities of flue gas in desulfurization tower at different inlet velocities and liquid–gas ratios. Velocity field distribution character was evaluated by uniformity index. The results showed that the flue gas forms a vortex in the tower and a local high-speed gas-flow appears in the empty tower, which led to a poor flow field uniformity. After adding the spray, the flow field is integrated into uniformity. The slurry has obvious integration effect on flue gas. The lower the inlet flue gas velocity is, the higher the velocity uniform index in the desulfurization tower will be, and the heat exchange between the two phases more sufficient. To achieve the same uniformity, the less amount of slurry is required while the inlet velocity is slower. The energy consumption and material consumption of the desulfurization system can be effectively reduced by reducing the import speed reasonably.

scholarly journals Visualizing Water Desaturation in Frozen Gas Diffusion Layers With Flow Field Segmentation via Synchrotron X-Ray Radiography

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuzhou Zhang ◽  
Ryan Anderson ◽  
Ning Zhu ◽  
Lifeng Zhang
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Water Distribution ◽  
Gas Flow ◽  
Cold Start ◽  
Gas Diffusion ◽  
Water Transfer ◽  
X Ray ◽  
Transfer Behavior ◽  
Field Geometry

Synchrotron X-ray tomography images were used to study dynamic, regional water transfer behavior in the gas diffusion layer (GDL) during thawing and desaturation processes. Initially saturated, frozen GDLs were thawed and desaturated with air in a serpentine gas flow channel. On-the-fly (OTF) high speed CT scans via synchrotron X-ray allowed the capture of consecutive water transfer inside the GDL under the cold start-up gas purging condition. Desaturation data of Sigracet 35AA GDLs with three superficial gas velocities (2.88–5.98 m/s) were selected for analysis. Multiple spatial segmentation levels based on the flow field geometry, including channel vs. rib, individual channels and ribs, and smaller sections in each channel and rib, were applied to the in-plane direction to study the GDL regional thawing and desaturation behaviors. Each segmentation volume had a similar desaturation pattern in general; however, water distribution and desaturation show heterogeneity over the GDL domain, as well as relation with factors including the flow field geometry, air traveling distance, and initial saturation level. These data from the segmentation analysis expand the knowledge of localized water transfer behavior during the cold start thawing process. These data can also provide valuable information for future cold start modeling and help in optimizing the PEM fuel cell flow field design.

Exact solutions for flow of a perfect gas in a two-dimensional Laval nozzle

1950 ◽  
Vol 203 (1075) ◽  
pp. 551-571 ◽  
Keyword(s):  
Flow Field ◽  
Exact Solutions ◽  
Infinite Series ◽  
Laval Nozzle ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Perfect Gas ◽  
Hodograph Method ◽  
Sonic Point ◽  
Subsonic Part

A family of exact solutions is found for the problem of steady irrotational isentropic shockfree transsonic flow of a perfect gas through a Laval nozzle in two dimensions. The hodograph method is used, whereby the position co-ordinates x , y are expressed in terms of the velocity variables; the expressions are infinite series in the subsonic part of the flow field, infinite integrals (analytic continuations of the series) in the supersonic part. An inversion is required to get the velocity as a function of position; in general, this requires detailed numerical calculations, but approximate formulae (62) are found for the neighbourhood of the sonic point on the axis.

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