Sine Wave Flow Research Articles

Numerical study on improved mass and heat transfer performance in a solid oxide electrolysis cell with sine wave flow field

In this paper, the periodic variation of sine wave is used to promote the transport and diffusion process of reactive gases; and the relationship between the performance of a solid oxide electrolysis cell (SOEC) and the mass and heat transfer capabilities of its flow field is thoroughly examined. The impact of variations in the amplitude and frequency of the sine wave on the SOEC's electrolysis efficiency, its mass and heat transfer properties, and fluid flow dynamics are explored. The results indicate that longitudinal flow velocity of the gas in the sine wave flow channel is increased by 26.96–80.76% at a current density of 10000 A/m2, and this kind of flow channel exhibits superior gas transport performance. Moreover, the temperature-uniformity index and the maximum thermal stress of the positive-electrolyte-negative (PEN) structure are decreases by 18.93–22.67% and 20%, respectively. It indicates that this configuration is capable of reducing thermal stress and enhancing the uniformity of temperature distribution at high current-densities. Increasing the amplitude and frequency improves the comprehensive performance of the flow field. More specifically, frequency has a greater impact on flow field performance than amplitude.

Wind Profiles in Peninsular Malaysia: A Comprehensive Upper Air Analysis

Understanding the atmospheric properties and patterns is crucial in empowering Malaysia's national aerospace blueprint, national space, and legislation. While various policies have been enacted and implemented, there is a lack of information on the wind profile, specifically the upper air across Peninsular Malaysia. Realising the need to establish a standard guideline for national reference, future research, space-aerospace application, and legislation, this study was performed to develop the first wind profile analysis of upper air in Peninsular Malaysia. Relevant data from the Malaysian Meteorology Department was collected for analysis and evaluation. Specifically, a meteorology balloon attached with a sounding radiosonde was used to record data at 0000UTC (0800 h LT) and 1200UTC (2000 h LT) on the 15th day of each month for 7 years (from 2015 to 2021) at the KLIA and Kuantan Meteorology Stations for the wind profiling analysis. The daily overall data collection was recorded accurately once the balloon's rising rate stabilises from vertical air current (katabatic or anabatic winds). Subsequently, the collected data were evaluated in terms of the minimum, maximum, and average wind speeds for each year and time. Finally, the average wind speed of each year and time were combined to generate the Peninsular Malaysia wind profile. Based on the results, the projected wind profile for both stations identified three peaks of discrete sine wave flow type with low-speed wind profile in Peninsular Malaysia. The three peaks amplified the highest air velocity, whereby the 1st and 2nd peaks were located at the troposphere layer from 9,000 m to 12,000 m altitude (average wind speed of 10.8 ms-1) and 12,000 m to 18,000 m altitude (average wind speed of 13.7 ms-1). The 3rd peak was located at the stratosphere layer from 18,000 m to 32,000 m altitude (average wind speed of 15.2 ms-1). Since East Malaysia is located on the same equatorial line, the wind profile is hypothetically the same and exhibits only slight differences. In short, the established wind profile of upper air in Peninsular Malaysia in this study would facilitate other future studies and assist long-term planning of Malaysia's airspace legislation.

Effects of a Dynamic Injection Flow Rate on Slug Generation in a Cross-Junction Square Microchannel

The injection flow rates of two liquid phases play a decisive role in the slug generation of the liquid-liquid slug flow. However, most injection flow rates so far have been constant. In order to investigate the effects of dynamic injection flow rates on the slug generation, including the slug size, separation distance and slug generation cycle time, a transient numerical model of a cross-junction square microchannel is established. The Volume of Fluid method is adopted to simulate the interface between two phases, i.e., butanol and water. The model is validated by experiments at a constant injection flow rate. Three different types of dynamic injection flow rates are applied for butanol, which are triangle, rectangular and sine wave flow rates. The dynamic injection flow rate cycles, which are related to the constant slug generation cycle time t0, are investigated. Results show that when the cycle of the disperse phase flow rate is larger than t0, the slug generation changes periodically, and the period is influenced by the cycle of the disperse phase flow rate. Among the three kinds of dynamic disperse flow rate, the rectangular wave influences the slug size most significantly, while the triangle wave influences the separation distance and the slug generation time more prominently.

The onset of turbulence in physiological pulsatile flow in a straight tube

An empirical correlation for the onset of turbulence in physiological pulsatile flow is presented. We pumped three different test fluids of kinematic viscosity 0.008–0.035 cm2/s through four straight tubes 0.4–3.0 cm in diameter. A Scotch yoke mechanism provided an oscillatory sine wave flow component of known stroke volume and frequency. We adjusted the mean flow independently until we detected signal instabilities from hot film wall shear stress probes. The critical peak Reynolds number was found to correlate with the Womersley parameter and the Strouhal number as a power law function with a root-mean-square (rms) error of 15.2%. Experimental measurements of the laminar velocity profile are compared to theoretical predictions from Poiseuille’s law and Womersley’s solution.

A new method for the calibration of peak flow meters

The objective of this paper is to assess the current methods for the calibration of peak flow meters and devise a method of producing a known flow with an inexpensive apparatus simple enough to be built from a set of dimensions. The methods currently available tend to be expensive and complex or impractical for routine use. The aim was that the wave form produced should approximate to a forced expiratory flow and be capable of being described in mathematical terms and be relatively inexpensive to produce. The resulting apparatus which has been built, produces a sine wave flow the peak of which can be set to any desired level and be determined to a high degree of accuracy. The apparatus can be built from a set of dimensions and is inexpensive. The apparatus is a primary and not a derived standard.

An in vitro study on the effect of branch points on the stability of coronary artery flow

Empirical correlations for the onset of turbulence in pulsatile flow through a straight tube and a 45° T-bifurcation are presented. We pumped three different test fluids of kinematic viscosity 0.008–0.035 cm 2 s −1 through four straight tubes 0.4–3.0 cm in diameter and three 45 degree T-bifurcations 0.45–2.2 cm in diameter. A Scotch yoke mechanism provided an oscillatory sine wave flow component of known stroke volume and frequency. To determine transition to turbulence, we adjusted the mean flow independently until we detected signal instabilities from hot film or electrochemical wall shear stress probes. The critical peak Reynolds number was found to correlate with two independent dimensionless groups: the Womersley parameter and the Strouhal number. We derived power law functions of these groups to provide an accurate and convenient method of predicting transition in both straight and bifurcating tubes. When compared to pulsatile flow through the straight tube, the presence of flow separation within the 45° T-bifurcation induced flow instabilities at lower values of the peak Reynolds number. The correlation for the 45° T-bifurcation is also a suitable model for predicting transition at coronary branch points, which we previously studied in an in vitro pulse duplicator. Flow instabilities at coronary branch points may play an important role in atherogenesis.

Wave and Turbulent Film Condensation on a Vertical Surface. Correlation for Average Heat-Transfer Coefficient.

The experimental study of body forced convection of pure vapor on a vertical surface (l=2980 mm) is presented. CFC11, CFC113 and HCFC123 are used as the working fluids. The flow patterns of condensate film are classified into four kinds of flow : L flow (laminar flow), L-S flow (laminar and sine wave flow), L-S-H folw (laminar, sine wave and harmonic wave flow), L-S-H-T flow (laminar, sine wave, harmonic wave and turbulent flow). The nondimensional correlations for predicting the average heat-transfer coefficients are obtained for four kinds of flow and compared with the experimental results, respectively. Assuming more simple four kinds of flow patterns, which are L flow, S flow (sine wave flow), H folw (harmonic wave flow) and T flow (turbulent flow), simple nondimensional correlations for predicting the average heat-transfer coefficients are also obtained for S flow, H flow and T flow. The nondimensional correlations for combined H and T flow are also obtained.

Wave and Turbulent Film Condensation on a Vertical Surface. Correlation for Local Heat-Transfer Coefficient.

The experimental study of body forced convection of pure vapor on a vertical surface (l=2980 mm) is presented. CFC11, CFC113 and HCFC123 are used as the working fluids. The flow patterns of condensate film are classified into four kinds of flow : L flow (laminar flow), L-S flow (laminar and sine wave flow), L-S-H folw (laminar, sine wave and harmonic wave flow), L-S-H-T flow (laminar, sine wave, harmonic wave and turbulent flow). The nondimensional correlations for predicting the average heat-transfer coefficients are obtained for four kinds of flow and compared with the experimental results, respectively. Assuming more simple four kinds of flow patterns, which are L flow, S flow (sine wave flow), H folw (harmonic wave flow) and T flow (turbulent flow), simple nondimensional correlations for predicting the average heat-transfer coefficients are also obtained for S flow, H flow and T flow. The nondimensional correlations for combined H and T flow are also obtained.

Assessment of total pulmonary airway resistance under mechanical ventilation

We propose a procedure for assessing the pulmonary airway resistance of patients under mechanical ventilation with a volume-cycled respirator having a sine-wave flow curve and inspiration/expiration (I/E) ratio of 1/2. This simplified procedure requires only the respirator's manometer and spirometer. The method is based on Ohm's Law, dividing the pressure difference (as shown on the manometer) between the peak value and that obtained by occluding the expiratory outlet by one-tenth of the minute volume (Vm). The relationship between the Vm and flow is obtained by calculating the height of the triangle formed by the sine wave, given that the area approximates total volume and the base is derived from the frequency and I/E ratio. This method was tested in 296 measurements on 106 patients using as a control the determination of resistance with a pneumotachograph and differential manometer placed between the patient and respirator. There was a high correlation (r = 0.96) between both procedures. To further facilitate bedside use, we have prepared a graph relating common values of Vm and pressure to resistance.

Phase detection electromagnetic flowmeter-design and use.

Two types of gated sine-wave electromagnetic flowmeter are examined critically, and found to be sensitive to phase shift in the transducer signal. This phase shift is always found in a sine-wave flow transducer because of imperfection in construction, particularly in those used for physiology and medicine. A flowmeter design that discards amplitude modulation and is sensitive to phase change only is described. Advantages over other types of electromagnetic flowmeter are discussed. Results obtained with the phase detection flowmeter are illustrated.

Device for the estimation of the rate of work on passing air by sine wave flow

In investigating the resistance to airflow of equipment for respiratory protection, it is often desirable to know the rate of work done in sine wave flow. A device is described which allows this estimation to be made without intermediate calculation from the results of simple experiments carried out under conditions of constant rates of flow. If these results, when plotted on logarithmic paper as pressure against rate of flow, lie on a straight line, the device allows a second line to be drawn which represents the rate of work done in sine wave flow plotted against the volume moved per minute.

Mass Transfer through an Inside Tube Wall to a Pulsation Flow

It was observed that mass transfer was greater in a pulsation flow than in a steady flow. As one of the simplest cases of mass transfer in a pulsation flow, we studied mass transfer through an inside tube wall to a pulsation flow, using a sample tube, whose inside wall was coated with β-naphthol. An experimental apparatus as shown in Fig. 1 was employed for the analyses of the systems. A piston type pulse generator was used for determining relationships between mass transfer and pulsation characteristics in the pulsation flow caused by superposing the "sine waveflow" on the steady flow.Experimental conditions were as follows(a) Flow condition; Apparent Re. number: 500-10, 000(b) Pulsation characteristics:Frequcncy: 100-500(cycle/min)Linear amplitude for l cycle: 0-2.0×10-1(m)(c) Dimensions of sample tubeLength: 0.3(m)Inside diameter: 1x10-2(m)The mass-transfer Coefficient kL(kg-mol/m2·hr·kg.mol/m3) and JD-factor were obtained from the experimental results, and are shown in Table l and Figs. 4 and 5.Conclusions:(1) Mass-transfer coefficient increases in direct proportion to the increase of amplitude and frequency, but in inverse proportion to that of Re. number.(2) The following equation represents the rate JD-factor increase, (Jp-J8/J8)D, as obtained by the dimensional analysis.(3) It is supposed that the charactristic increment of mass transfer in the pulsation increase in turbulency, affecting such flow conditions as frequency and amplitude.