The Effect of Silencers of the Helmholtz-Resonator Type on Pressure Waves of Finite Amplitude: Single Pressure Pulses

1974 ◽  
Vol 16 (4) ◽  
pp. 268-275 ◽  
Author(s):  
G. H. Trengrouse
Keyword(s):  
Incident Wave ◽  
Helmholtz Resonator ◽  
Single Pulse ◽  
Finite Amplitude ◽  
Pressure Waves ◽  
Flow Conditions ◽  
Partial Reflection ◽  
One Dimensional ◽  
The Relationship ◽  
Good Agreement

The attenuation of large-amplitude waves effected by silencers of the so-called Helmholtz-resonator type is envisaged as being due to the finite efflux of gas through the holes of the silencer with resulting partial reflection, and hence reduced transmission, of the incident wave. Quasi-steady, one-dimensional flow arguments are used to predict the attenuation, the flow conditions being assumed reversible and adiabatic, that is, isentropic. This latter assumption is avoided in an alternative method by assuming a knowledge of the relationship between pipe Mach numbers and the pressure difference in the pipe across the holes. Indicator diagrams resulting from single pulse experiments are, in general, in good agreement with those predicted.

Effect of Sudden Changes in Flow Area on Pressure Waves of Finite Amplitude

1966 ◽  
Vol 8 (2) ◽  
pp. 198-206 ◽  
Author(s):  
G. H. Trengrouse ◽  
M. M. Soliman
Keyword(s):  
Steady Flow ◽  
Finite Amplitude ◽  
Theoretical Treatment ◽  
Pressure Waves ◽  
Flow Conditions ◽  
Flow Area ◽  
One Dimensional ◽  
Isentropic Flow ◽  
Flow Through ◽  
Flow Experiments

Previous investigations of the flow of gases through sudden area changes in pipes are briefly reviewed, both unsteady and steady flow conditions being considered. The present paper concerns the effects of such area changes on single pressure waves of finite amplitude, and covers incident wave amplitudes greatly in excess of those previously investigated. Theoretically, the flow at the area change is assumed to be quasi-steady and one-dimensional, and two alternative treatments are presented. These are based respectively on reversible adiabatic (isentropic) and, more accurately, irreversible adiabatic conditions. Experiments using a simple shock tube confirm the validity of the more accurate theoretical treatment over the range of area and incident pressure ratios considered, namely, 8.1 and 2.4 respectively. The theoretical treatment based on the assumption of isentropic flow at the section change, however, is inadequate in some respects. Discrepancies between theory and experiment are observed when considering, firstly, the reflected wave at an enlargement and, secondly, the transmitted wave at a contraction. Steady flow experiments in which the discharge coefficient for flow through a sudden contraction is measured are also described, this coefficient being required in the theoretical analysis.

Control strategy optimization for a dual-clutch transmission downshift with a single slipping clutch during the torque phase

2017 ◽  
Vol 232 (5) ◽  
pp. 651-666 ◽  
Author(s):  
Jikai Liu ◽  
Biao Ma ◽  
Heyan Li ◽  
Man Chen ◽  
Guoqiang Li
Keyword(s):  
Control Strategy ◽  
Power Flow ◽  
Control Strategies ◽  
Poor Quality ◽  
Dual Clutch Transmission ◽  
Flow Conditions ◽  
Robust Controller ◽  
Simulation Results ◽  
The Relationship ◽  
Good Agreement

During the torque phase, appropriate coordination between two clutches is of vital importance to the dual-clutch transmission so that a high-quality shift is achieved without clutch interaction and engine flare, because a poor-quality shift definitely extends the shift time and increases the friction work. Concerning this problem, two different power flow conditions during the torque phase are discussed in detail, after investigation of the dual-clutch transmission downshift process and the design of an H∞ robust controller for the inertia phase. The results obtained indicate that, if two clutches are slipping simultaneously during the torque phase, either power interruption or power circulation occurs. Thus, by optimizing the relationship between the two clutches, a novel control strategy is proposed for the dual-clutch transmission so that the downshift process is accomplished with only one slipping clutch, in order to obtain the highest system efficiency. The system model was established on the MATLAB/Simulink platform and used to study the variations in the torque and the speed output in response to different control strategies. The simulation results show that, with the smooth inertia phase guaranteed by the robust controller, the proposed control strategy not only can avoid power interruption or power circulation during the torque phase but also can shorten the shift time (from 1.1 s to 0.8 s) and reduce the jerk level (from 6.8 m/s3 to 5.7 m/s3) effectively, in comparison with the conventional control strategy. Finally, to validate the effectiveness of the proposed control strategy, bench tests on a dual-clutch transmission were carried out, and the test data obtained show good agreement with the simulation results.

Numerical Study of Turbulent Flows Through a Circular Duct With a Rotating Fan

2009 ◽  
Author(s):  
Gaurav Rajwade ◽  
Jie Cui
Keyword(s):  
Turbulent Flows ◽  
Numerical Study ◽  
Pressure Rise ◽  
Flow Conditions ◽  
Circular Duct ◽  
Flow Information ◽  
Computational Fluid Dynamics Cfd ◽  
Air Circulation ◽  
The Relationship ◽  
Good Agreement

A fan is an important part for air circulation in household appliances and automobiles. In this research an attempt has been made to extract the flow information using the Computational Fluid Dynamics (CFD) technique. The numerical results were found for a case with a stationary fan inside the duct and the data obtained were in good agreement with the experiment. The evolution of velocity profiles at various axial locations for different flow conditions were also studied in this research. The numerical method was then extended to the cases with a rotating fan. A proof-of-concept run was also successfully carried out to showe the relationship between air flow rate in the duct and the corresponding pressure rise.

Subsonic Elector Nozzle Limiting Flow Conditions

2003 ◽  
Vol 125 (3) ◽  
pp. 851-854 ◽  
Author(s):  
L. J. De Chant
Keyword(s):  
Design Space ◽  
Reverse Flow ◽  
Control Volume ◽  
Flow Conditions ◽  
Efficient Tool ◽  
One Dimensional ◽  
Choked Flow ◽  
Ejector Nozzle ◽  
Classical Control ◽  
Good Agreement

This paper describes an analytical method used to provide information concerning limiting flows for subsonic ejector nozzles. Three potential limiting flows have been identified and modeled using reduced control volume based analysis: (1) incipient reverse flow into the secondary inlet, (2) choked flow in the secondary inlet, and (3) choked flow in the exit mixing stream. Comparison of the methods developed here with the classical control volume portion of an ejector nozzle code have been performed and show good agreement. As such, it is concluded, that within the scope of one-dimensional control-volume based computations, that the methods developed here provide an efficient tool to help delimit the design space acceptable for ejector operation.

scholarly journals Design of Ultrasonic Transducer for Secondary Wave Generations with High Directivity

2019 ◽  
Vol 24 (4) ◽  
pp. 744-748
Author(s):  
Chol-Hak Kim ◽  
Myong-Jin Kim ◽  
Chol-Su Ri
Keyword(s):  
Natural Frequencies ◽  
Ultrasonic Transducer ◽  
Nonlinear Effects ◽  
Finite Amplitude ◽  
Ultrasonic Waves ◽  
Secondary Wave ◽  
One Dimensional ◽  
Resonance Frequencies ◽  
The Difference ◽  
Good Agreement

In this paper, we described a method of designing ultrasonic transducer which simultaneously radiates two finite-amplitude ultrasonic waves to produce the secondary waves with high directivity. For nonlinear effects, it is necessary that the frequencies of two primary waves are coincident with natural frequencies of the ultrasonic transducer. The main problem here is to predict the resonance frequencies of the first mode as well as higher modes. While the first resonance frequency of the transducer can be estimated easily, it is not trivial to do higher ones. When the length of transducer is much greater than its diameter, this problem is reduced to one-dimensional and higher mode frequencies are nothing but multiples of the first mode frequency. However, such a case is seldom encountered. Using the transfer matrix method, we obtained the resonance frequencies of the transducer analytically and compared these with numerical results from the simulation. The theoretical and simulation results are in good agreement with the difference of 3--6 kHz.

scholarly journals Mechanisms and Countermeasures on Sediment and Wood Damage in Sediment Retarding Basins

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3283
Author(s):  
Norio Harada ◽  
Kana Nakatani ◽  
Ichiro Kimura ◽  
Yoshifumi Satofuka ◽  
Takahisa Mizuyama
Keyword(s):  
Debris Flow ◽  
Flood Damage ◽  
Bed Load ◽  
Dimensional Model ◽  
Flow Conditions ◽  
One Dimensional ◽  
Wood Debris ◽  
Debris Transport ◽  
Sediment Flow ◽  
Good Agreement

Improvements in sediment retarding basin design are required to mitigate flood damage caused by bed load and wood debris outflow in lower river reaches. We used a scaled sediment retarding basin model to optimize our basin design, with the goal of improving sediment and wood debris transport and capture. Changes to the structural dimensions and elements of the sediment retarding basin were assessed under experimental debris flow conditions. The results obtained from the experiments and simulations were in good agreement regarding sediment flow and containment. The proposed one-dimensional model is useful for showing the effects of flow conditions within a sediment retarding basin on sediment transport.

Cascade Performance From Tests With Wheel of Axial Outlet

1964 ◽  
Vol 86 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Gunnar O. Ohlsson
Keyword(s):  
Dimensional Analysis ◽  
Flow Conditions ◽  
Blade Height ◽  
One Dimensional ◽  
Torque Measurements ◽  
Overall Performance ◽  
Axial Turbines ◽  
The Relationship

A method of determining overall cascade performance by means of torque measurements on a wheel with axial outlet is given. The method, which is believed to be new, is particularly suited for small axial turbines or compressors. It gives the overall performance in actual turbomachines and includes all losses. The method is simpler and gives more accurate results than the elaborate method of traversing, for instance, in small axial turbomachines with blade height below 0.1 inch. A one dimensional analysis is given and applied to two known flow conditions in order to obtain a comparison with other ways of evaluating these flow conditions. The relationship between cascade efficiencies defined in different ways is shown, and an illustrative example is given.

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

2003 ◽  
Vol 3 (1-2) ◽  
pp. 201-207
Author(s):  
H. Nagaoka ◽  
T. Nakano ◽  
D. Akimoto
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Turbulence Model ◽  
Uptake Rate ◽  
Oscillatory Flow ◽  
Substrate Uptake ◽  
Flow Conditions ◽  
Mass Transfer Mechanism ◽  
Substrate Uptake Rate ◽  
Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

‘Each Song Was Just Like a Little Sermon’

2018 ◽  
Author(s):  
Isaac Land
Keyword(s):  
Nineteenth Century ◽  
Golden Age ◽  
Military Training ◽  
One Dimensional ◽  
National Pride ◽  
Recent Scholarship ◽  
The Relationship

This chapter is central to the volume’s chronological contentions, as its argument accounts for the specialized, one-dimensional Dibdin of ‘Tom Bowling’ that has endured into recent scholarship. Focusing on Dibdin’s posthumous reception, it examines the moral and rhetorical difficulties of repackaging Dibdin’s works for a Victorian sensibility; it explores the specifics of mid-century concert culture previously highlighted by Derek Scott and William Weber as central to changes in nineteenth-century taste and programming; and it develops the theme of nostalgia into a revelatory consideration of the relationship between new naval technologies, national pride, and military training, and the songs, people, and language of a remembered Napoleonic ‘golden age’—to which Dibdin proves to have been as central, in the Victorian imagination, as Nelson.

Sign in / Sign up

Export Citation Format

Share Document