共查询到20条相似文献,搜索用时 31 毫秒
1.
A mathematical model for large amplitude wave propagation in a thin walled distensible tube is developed. The tube wall is considered as a membranic shell made of an incompressible, non-linear viscoelastic material with cylindrical orthotropy. The fluid is regarded as incompressible and inviscid and the flow is quasi-one-dimensional. The case of a pressure step applied at one end of a uniform straight tube is solved as an example. The system of partial differential equations, describing the motions of the fluid and the wall, are integrated numerically by using a two-step explicit scheme. Flow and deformation variables as well as the wave velocity are determined in time and space. 相似文献
2.
3.
4.
Summary The peristaltic mechanism of a Jeffrey fluid in a circular tube is investigated. The rheological effects and compressibility
of the fluid are taken into account. The modeled equations are solved using perturbation technique when the ratio of the wave
amplitude to the radius of the pore is small. In the second order approximation, a net flow due to a travelling wave is obtained
and effects of Reynolds number, relaxation and retardation times, compressibility of the fluid and tube radius are studied.
It is noticed that for the Jeffrey fluid the back flow only occurs for large values of the relaxation time and small values
of the retardation time (less than 10 in the present analysis). Another interesting observation is that oscillatory behavior
of the net flow rate in the Jeffrey fluid is less than that of a Maxwell fluid. Several results of other fluid models can
be deduced as the limiting cases of our situation. 相似文献
5.
6.
在焓流理论的基础上提出脉管制冷机的线性气流速度分析法,该方法着重求解脉管内气流速度的幅值和相位,给出的公式简单,概念直观,计算量少。对基本型、小孔型和双向进气型脉管进行了分析,获得的结果与数值模拟结果相似,说明了这是一种行之有效的分析方法。 相似文献
7.
A. K. Bajaj 《Dynamical Systems: An International Journal》1987,2(1):19-41
The nonlinear dynamics of a cantilever tube conveying a pulsatile flow and undergoing planar motions is investigated. The mean flow is near its critical value at which the downward vertical position of the tube gets unstable by flutter and executes limit-cycle oscillations. The pulsations in the flow are assumed to be small and harmonic with frequency nearly twice that of the limit cycle. To study the nonlinear dynamics, the method of averaging is utilized and the governing partial differential equation is reduced to a dynamic system on the plane. These two first-order differential equations depend on three parameters and govern the dynamics of the amplitude of motion of the tube. The planar system is studied for its qualitative behaviour using ideas from the local bifurcation theory and a local bifurcation set in the parameter plane is constructed. Using ideas from codimension-two unfolding of singularities, this bifurcation set is further refined. The resulting partial bifurcation set and the associated phase portraits in the various regions of the flowrate-detuning parameter plane show that the averaged equations have constant as well as periodic solutions. The stabifity type and the number of these solutions changes from one region to another. This explains how periodic or 'phase-locked' oscillations of the cantilever tube bifurcate into amplitude-modulated or almost-periodic motions. 相似文献
8.
Katsunori Ishii Masahiro Suzuki Tomoomi Segawa Yoshiyuki Kihara Masatoshi Yasuda Shuji Matsusaka 《Advanced Powder Technology》2011,22(4):522-525
To reduce the sample amount required for the measurement and evaluation of particle flowability, a simple method has been developed through experimental research. The principle of this measurement is based on the vibrating tube method. The sample particles used in the experiment were pulverized ZrO2 and granulated WO3 with different concentration of fine particles. After a small amount of sample particles were put into a tube, vibration was applied at a constant frequency and amplitude, and the mass of particles discharged from the tube was measured at constant time intervals. The experimental results showed that the minimum sample amount required for the measurement to evaluate the particle flowability was 10 g. The factors to evaluate the flowability in this simple vibrating tube method were the flow time and the characteristic mass flow rate. 相似文献
9.
双向进气型脉管制冷机的线性理论分析 总被引:1,自引:0,他引:1
采用线性模型对双向进气型脉管制冷机的性能进行了分析.得到了通过回热器的焓流、质量流量及脉管冷端压力和流量相位差的代数计算公式.详细分析了工作频率对脉管制冷机制冷量与COP的影响,并对额定输入压力振幅和额定输入功率两种工况分别进行了优化分析.所得结果与其它文献完全一致. 相似文献
10.
科氏质量流量计模拟驱动方法研究 总被引:1,自引:0,他引:1
驱动系统是科里奥利质量流量计的重要组成部分之一。它为流量管提供驱动力,使流量管以其固有频率和稳定的振幅振动,并且能够跟随流量管固有频率的变化而变化。目前的驱动系统是基于模拟信号的工作方式。分析了这种驱动系统的工作原理,比较了各种波形的驱动信号,研究了几种驱动电路。 相似文献
11.
G.Q LuP Cheng 《低温学》2002,42(5):287-293
An experimental investigation has been carried out on dynamical pressures of the viscous compressible flow oscillating at different locations in a Gifford-McMahon (G-M) type pulse tube refrigerator operating at cycle-steady states. Measurements show that the oscillating amplitude of the pressure was largest at the hot end of the regenerator while the cycle-averaged pressure was the largest in the reservoir. The latter characteristics can be explained based on a cycle-averaged and cross-sectional averaged of the governing equations for a compressible viscous oscillating flow. The reason why the cycle-averaged pressure of the compressible flow oscillating at low frequencies in a tube increases from the wave generator toward the reservoir is analyzed. In addition, the effect of the cycle-averaged pressure on the refrigeration performance is discussed, which can be used to explain why the system with proper asymmetric charging and discharging periods has a better performance than a symmetric one in a G-M type pulse tube refrigerator. 相似文献
12.
Summary In real systems there is always a certain amount of slip, which, however, is hard to detect experimentally because of the
required space resolution. In this paper, we analyze the effect of slip boundary conditions on the dynamics of fluids in porous
media by studying the flow of a Newtonian and non-Newtonian Maxwellian fluid in an axisymmetric cylindrical tube (pore), in
which the flow is induced by traveling transversal waves on the tube wall. Like in peristaltic pumping, the traveling transversal
waves induce a net flow of the liquid inside the pore. The viscosity as well as the compressibility of the liquid is taken
into account. This problem has numerous applications in various branches of science, including stimulation of fluid flow in
porous media under the effect of elastic waves and studies of blood flow dynamics in living creatures. The Navier-Stokes equations
for an axisymmetric cylindrical pore are solved by means of a perturbation analysis, in which the ratio of the wave amplitude
to the radius of the pore is small parameter. In the second order approximation, a net flow induced by the traveling wave
is calculated for various values of the compressibility of the liquid, relaxation time and Knudsen number. The calculations
disclose that the compressibility of the liquid, Knudsen number of slip flow and non-Newtonian effects in presence of peristaltic
transport have a strong influence of the net flow rate. The effects of all parameters of the problem are numerically discussed
and graphically explained. 相似文献
13.
14.
为了校准涡轮流量计的时间常数,建立液体阶跃流量试验装置,该装置利用螺杆泵输送流体形成平台流量,采用内啮合齿轮泵输送流体形成阶跃流量分量,通过控制高速电磁阀的开启与关闭实现阶跃流量分量与平台流量的叠加,最终产生阶跃流量。利用皮托管对阶跃流量产生时间进行评估,结果表明阶跃流量上升时间小于9 ms。在不同阶跃工况下对涡轮流量计开展时间常数校准试验,结果表明:涡轮流量计时间常数并非固定值,且受平台流量影响较大,具有随前平台流量增大而减小的趋势,受阶跃流量幅度影响较小;在小流量范围内,实际测量得到的动态流量系数与理论模型推导得到的动态流量系数偏差较大,而在大流量范围内二者较为吻合。最后对时间常数校准结果进行了不确定度评估,最大扩展不确定度约为10 ms(k=2)。研究成果有助于评估流量计动态特性,有望提高非稳态流量测量的准确度。 相似文献
15.
Abstract Crossflow induced vibrations of a triangular tube array with a pitch ratio 1.33 were investigated experimentally. The streamwise and cross‐stream displacements of a monitored tube in the array were simultaneously measured by two accelerometers to examine the tube response to the cross flow in a water tunnel. The experiment was aimed to study the effects of the array orientation, and the tube's natural frequency on the flow induced vibration of the tube array. It is shown by amplitude diagrams that fluid elastic vibrations exist when the reduced velocity is above a critical value. The critical reduced velocity is found to be sensitive to the orientation of the test array. Based on the measured data of critical reduced velocity, the tube array in a triangular pattern (at a 30‐deg orientation with respect to the flow direction in the experiment) is found to be more stable than when in a rotated triangular pattern (0‐deg orientation). Furthermore, it is illustrated that the discrepancy in natural frequency of the tubes delays the occurrence of the fluid elastic vibrations of the tube array. With all the tubes in the test array having the same natural frequency, the orbits of the tube that exhibits fluid elastic vibrations are an organized, elliptic shape. The corresponding spectra are line‐dominated with peaks at the natural frequency and its harmonics, suggesting that the tube vibration is an organized oscillator. Without the same natural frequency as the surrounding tubes, the monitored tube exhibits fluid elastic vibration at larger reduced velocity, vibrating in a relatively random orbit. 相似文献
16.
Whittaker RJ Heil M Waters SL 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1947):2989-3006
Motivated by the problem of self-excited oscillations in fluid-filled collapsible tubes, we examine the flow structure and energy budget of flow through an elastic-walled tube. Specifically, we consider the case in which a background axial flow is perturbed by prescribed small-amplitude high-frequency long-wavelength oscillations of the tube wall, with a slowly growing or decaying amplitude. We use a multiple-scale analysis to show that, at leading order, we recover the constant-amplitude equations derived by Whittaker et al. (Whittaker et al. 2010 J. Fluid Mech. 648, 83-121. (doi:10.1017/S0022112009992904)) with the effects of growth or decay entering only at first order. We also quantify the effects on the flow structure and energy budget. Finally, we discuss how our results are needed to understand and predict an instability that can lead to self-excited oscillations in collapsible-tube systems. 相似文献
17.
On-line sample concentration by evaporation through a narrow-bore membrane tube is described. The device can be deployed just prior to the detector or the sample may be concentrated prior to injection. As solution flows through a solvent-permeable membrane tube, (heated) drying gas (nitrogen/air) flows outside it to remove the solvent. The removal rate increases with increasing sample residence time, drying gas flow rate, and temperature. Various membranes and three concentrator designs (a rectangular maze, a serpentine and a filament-filled helix, the last performing the best) were fabricated and tested for post- and preseparation applications in suppressed anion chromatography. An order of magnitude concentration factors are readily obtained. The present system involves active mass transport radially outward through the walls of a tube. This is a system in which many of the traditional paradigms of flow through a tubular conduit no longer hold true. Because the flow rate continuously varies along the tube, residence time does not scale linearly with residence volume or conduit length. The effects of such mass transport on the parabolic velocity profile of laminar flow remain unknown. 相似文献
18.
基于流固耦合问题的弱耦合法,研究弹性管束不同流速的壳程或/和管程流体诱导下的振动响应。研究表明,流体诱导振动幅值随壳程或/和管程流速的增加而增加。与相同管程流速条件相比,壳程流体引起的振幅较大。随壳程流速增加监测点振动频率增加;随管程流速增加监测点振动频率基本不变。壳、管程流体耦合诱导的振动位移曲线与仅壳程流体诱导的振动位移曲线类似,说明弹性管束工作过程中的振动主要由壳程流体诱导。流体诱导的振动频率接近管束第一阶固有频率时,监测点在y、z方向振幅逐渐趋于峰值。流体诱导弹性管束的振动主要表现为面内振动。 相似文献
19.
B. M. Galitseiskii Yu. A. Ryzhov E. V. Yakush 《Journal of Engineering Physics and Thermophysics》1975,29(1):835-839
The results of measurements of the attenuation factor of the amplitude of pressure and velocity oscillations in a pulsating nonisothermal turbulent flow of air in a cylindrical tube close to the first resonance harmonic (80 ± 5 Hz) are presented. 相似文献
20.
《低温学》2002,42(3-4):209-221
The rate of refrigeration of the inertance pulse tube (IPTR) is found as a function of the relevant parameters. In the simplified case of infinite volume of the reservoir and zero dead volume of the regenerator, these parameters are the dimensions of the inertance tube, the volume of the pulse tube, the conductance of the regenerator, the driving pressure, and the frequency. The effective conductance of the inertance tube is determined using a simple turbulent flow model. It is found that the performance of the IPTR is superior to that of the orifice pulse tube refrigerator (OPTR) over a limited range of frequencies. The improvement is explained in terms of the pressure amplitude in the pulse tube, the flow rate between the regenerator and the pulse tube, and the phase angle between these parameters. The analysis is extended to the case of finite reservoir and regenerator volumes. It is indicated how the results obtained can be useful in experimental work. 相似文献