Experimental studies on the flow velocity of molten metals in a ladle model at centric gas blowing

1992 ◽  
Vol 63 (3) ◽  
pp. 93-104 ◽  
Author(s):  
Yongkun Xie ◽  
Franz Oeters
Keyword(s):  
Flow Velocity ◽  
Experimental Studies ◽  
Molten Metals ◽  
Gas Blowing

Experimental Studies on Loads Acting on Two Piles of Side-by-Side Arrangements in the Uniform Flow

2012 ◽  
Vol 226-228 ◽  
pp. 1785-1788
Author(s):  
Zhao Qing Zhu ◽  
Guo Liang Dai
Keyword(s):  
Drag Coefficient ◽  
Flow Velocity ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Drag Forces ◽  
Pile Diameter ◽  
Two Component ◽  
Balance Analysis ◽  
Different Diameters

Indoor model experiments were made to study drag loads on two piles of side-by-side arrangements in the uniform flow. Take three different velocities of the flow, three different diameters of piles and five different distances of two piles in the experiments to get the variations of loads. Drag forces were measured by a two-component balance. Analysis on experiment results shows that drag forces increase with the increase of the pile diameter, the increase of the flow velocity and the decrease of the distance of two piles. The drag coefficient CDunder different Reynolds numbers shows the same change law. The drag coefficient CDdecreases with the increase of the distance of two piles and has good coherence to the ratio of the distance of two piles to the pile diameter.

Flow Field and Heat Transfer of an Impinging Synthetic Jet in the Presence of Cross-Flow: Application of SAS and DES Approaches

2021 ◽  
pp. 095440892110644
Author(s):  
Farzad Bazdidi–Tehrani ◽  
Ali Saadniya ◽  
Soroush Rashidzadeh
Keyword(s):  
Heat Transfer ◽  
Flow Velocity ◽  
Active Flow Control ◽  
Experimental Studies ◽  
Cross Flow ◽  
Numerical Data ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Detached Eddy Simulation ◽  
Cross Flow Velocity

Nowadays, synthetic jets have various applications such as cooling enhancement and active flow control. In the present paper, the capability of two turbulence modelling approaches in predicting thermal performance of an impinging synthetic jet is investigated. These two approaches are scale adaptive simulation (SAS) and detached eddy simulation (DES). Comparisons between numerical data and experimental studies reveal that the ability of DES in predicting the asymmetrical trend of heat transfer profiles is better than SAS in almost all the study cases. Although, near the stagnation zone, the performance of SAS is superior. Results show that the effects of parameters such as frequency, cross-flow velocity and suction duty cycle factor are well predicted by both approaches. An increase of cross-flow velocity from 1.81 m/s to 2.26 m/s results in an improvement of [Formula: see text] near the stagnation point by almost 16.3% and 9.2% using DES and SAS, respectively.

Absolute/Convective Instability Transition in a Backward Facing Step Combustor: Fundamental Mechanism and Influence of Density Gradient

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Kiran Manoharan ◽  
Santosh Hemchandra
Keyword(s):  
Stability Analysis ◽  
Flow Field ◽  
Flow Velocity ◽  
Convective Instability ◽  
Hydrodynamic Instability ◽  
Combustion Instability ◽  
Experimental Studies ◽  
Base Flow ◽  
Flow Density ◽  
Backward Facing Step

Hydrodynamic instabilities of the flow field in lean premixed gas turbine combustors can generate velocity perturbations that wrinkle and distort the flame sheet over length scales that are smaller than the flame length. The resultant heat release oscillations can then potentially result in combustion instability. Thus, it is essential to understand the hydrodynamic instability characteristics of the combustor flow field in order to understand its overall influence on combustion instability characteristics. To this end, this paper elucidates the role of fluctuating vorticity production from a linear hydrodynamic stability analysis as the key mechanism promoting absolute/convective instability transitions in shear layers occurring in the flow behind a backward facing step. These results are obtained within the framework of an inviscid, incompressible, local temporal and spatio-temporal stability analysis. Vorticity fluctuations in this limit result from interaction between two competing mechanisms—(1) production from interaction between velocity perturbations and the base flow vorticity gradient and (2) baroclinic torque in the presence of base flow density gradients. This interaction has a significant effect on hydrodynamic instability characteristics when the base flow density and velocity gradients are colocated. Regions in the space of parameters characterizing the base flow velocity profile, i.e., shear layer thickness and ratio of forward to reverse flow velocity, corresponding to convective and absolute instability are identified. The implications of the present results on understanding prior experimental studies of combustion instability in backward facing step combustors and hydrodynamic instability in other flows such as heated jets and bluff body stabilized flames is discussed.

Catalytic Combustion of Ultra-Low Heating Value Fuels Over 0.5%Pd/ZrO2/γ-Al2O3 Catalyst

2017 ◽  
Author(s):  
Xiaojing Lv ◽  
Xiaoyi Ding ◽  
Yiwu Weng
Keyword(s):  
Flow Velocity ◽  
Ignition Temperature ◽  
Catalytic Combustion ◽  
Experimental Studies ◽  
Wood Chip ◽  
Inlet Temperature ◽  
Technology Application ◽  
Gas Concentration ◽  
Combustible Gas ◽  
Heat Value

Catalytic combustion of ultra-low heat value fuel over 0.5%Pd/ZrO2/γ-Al2O3 was investigated to offer an opportunity for scientifically using such fuel sources. The experimental studies were performed using single fuel, synthetic mixtures and different kinds of gasified biomasses, respectively. The effects of varied combustible gas concentration, inlet temperature and flow velocity on the conversion rate were also studied. The results showed that the ignition temperature of 1.4% CH4 over the catalyst used is lower 210 °C than that in the oxidation absence of catalyst. Conversion of CH4 increased with decreasing flow velocity and increasing combustible gas concentration. The influence of the flow velocity on the conversation is more significant when further increasing the CH4 concentration to a certain degree. The ignition temperature for CO, H2, CH4 decreased with increasing concentration, and the specific order is TCH4, TCO, TH2. The experimental data showed that the influence of H2 is very obvious for CH4 combustion-supporting character by adding different concentration of H2. Among the experiments of three kinds of gasified biomasses, the catalytic combustion characteristics of wood chip gas is best, followed by grape seed gas and cotton wood gas. These studies would provide the experimental analysis and technical support for catalytic combustion technology application in ultra-low heat value fuel.

Numerical and Experimental Studies on DNA Combing Used in Fabricating Nanochannel Electroporation (NEP) Chips

2012 ◽  
Vol 586 ◽  
pp. 421-429 ◽  
Author(s):  
Samuel I En Lin
Keyword(s):  
Flow Velocity ◽  
Experimental Studies ◽  
Cell Manipulation ◽  
Dna Stretching ◽  
Velocity Difference ◽  
Two Phase ◽  
Pdms Stamp ◽  
Yield Rate ◽  
Dna Combing ◽  
Micro Pillars

Microelectromechanical processes were used to generate a stamp with array of micro pillars. This stamp was subjected to DNA combing and imprinting to form nanostrands between the micro pillars, followed by sputter coating with gold, vapour deposition and imprinting processes in order to produce the required nanochannels for the gene chip. These preparation processes have been widely used to create implementations for cell manipulation and electroporation. However, the underlying mechanism of DNA stretching has only been demonstrated experimentally and is not fully understood. It, therefore, arrives unstable yield rate when process parameters are changed. This study investigated the DNA combing and imprinting processes using two-phase flow and moving mesh methods to analyse the variation of flow field at the micron level. It shows that while withdrawing from water, a smaller velocity difference in each location and the velocity difference of pillars are the major determinants of DNA stretching and curing. The simulation results showed that a bigger α and θ led to a greater difference in flow velocity on the PDMS stamp surface; greater flow velocity difference could affect the adhesion of DNA (subsequently compromising the formation of the nanochannels). As suggested by our experimental data, longer nanochannels (3 μm) displayed a wider range of stretching speed with yield rate >90%.

scholarly journals A Computational Study on the Damping-Amplitude Dependence and Estimation of the Limit Cycle Oscillations for Normal Triangular Arrays with One Tube Undergoing Fluidelastic Instability

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1498
Author(s):  
Beatriz de Pedro ◽  
Guillermo Laine ◽  
Luis Tufiño ◽  
Jorge Parrondo
Keyword(s):  
Flow Velocity ◽  
Limit Cycle ◽  
Vibration Amplitude ◽  
Computational Study ◽  
Experimental Studies ◽  
Amplitude Dependence ◽  
Limit Cycle Oscillations ◽  
Cfd Model ◽  
Time Step ◽  
Fluidelastic Instability

While the estimation of the critical velocity for fluidelastic instability of tube arrays has received considerable attention for decades, the studies intended to analyze the post-stable behavior have been scarce. However, the behavior of the system under instability, is also interesting in order to characterize the amount of energy transferred from fluid to structure. A computational study has been carried out for the case of one tube vibrating in a normal triangular array by means of a CFD model previously developed with Fluent by the authors. This model incorporates the motion of the vibrating tube by means of user defined functions for both forced and free oscillations, so that the tube position can be updated and the mesh rebuilt at every time step. First, predictions of limit-cycle oscillations (zero net damping) were obtained for pitch ratios P/d = 1.25 and 1.375, so that the experimental response curves (amplitude against flow velocity) measured in other experimental studies could be used for contrast purposes. After validation, the CFD model was used to investigate how the net damping of the fluid-structure system depends on the vibration amplitude for a given flow velocity, which shows the non-linear nature of the tube response. Finally, special simulation series were conducted to explore the effects of pitch ratio, Reynolds number and structural damping on the net damping of the system for constant vibration amplitude.

Sheet cathode design and experimental study on the electrochemical machining of deep narrow slots in TB6 titanium alloy

2019 ◽  
Vol 234 (4) ◽  
pp. 801-813
Author(s):  
Feng Wang ◽  
Jianshe Zhao ◽  
Yanming Lv ◽  
Xiuqing Fu ◽  
Min Kang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Flow Velocity ◽  
Experimental Studies ◽  
Electrochemical Machining ◽  
Low Frequency ◽  
Specific Strength ◽  
Cathode Design ◽  
Narrow Slot ◽  
Tb6 Titanium Alloy ◽  
Side Gap

TB6 titanium alloy is extensively applied in lightweight vehicles, biomedicine, and other domains because of its high specific strength, excellent fracture toughness, and excellent corrosion resistance. Electrochemical machining is a non-contact processing technology that has significant advantages in processing materials that are difficult to cut, such as cemented carbide, high-temperature alloys, and titanium alloys. To improve the consistency of deep narrow slots fabricated in TB6 titanium alloy via electrochemical machining, a sheet cathode design and experimental studies were carried out in this work. Based on a unidirectional fluid–structure coupling simulation, the influence of the stiffener arrangement on the cathode rigidity and flow-velocity distribution was studied. Furthermore, by modifying the geometry of the stiffener, the cathode deformation was significantly reduced, and flow-velocity uniformity at the cathode outlet was improved. The influence of a superimposed low-frequency oscillation on the gap distribution and the profile error of a deep narrow slot was investigated experimentally. The results revealed that when an applied voltage of 24 V, an oscillation frequency of 50 Hz, and an amplitude of 0.05 mm were adopted, a highly homogeneous deep narrow slot with an entrance gap of 0.24 mm and a side gap of 0.33 mm was machined into the TB6 titanium alloy.

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