Mass flow rate control system for time-dependent laminar and turbulent flow investigations

Durst, F.; Heim, U; Ünsal, Bülent; Kullik, G

doi:10.1088/0957-0233/14/7/301

Cited by 55 publications

(32 citation statements)

References 8 publications

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“…The experimental set-up, including the mass-flow-rate control unit (see figure 1), used in the present investigations, was explained in detail by Durst et al (2003) and Durst &Ünsal (2006). Therefore, only a brief description will be given here for …”

Section: Test Rig Triggering Device and Measurement Equipmentmentioning

confidence: 99%

“…This allowed different Reynolds numbers to be set and the preset flow rate to be maintained for each of the investigations. Due to the critical valve operation principle of the MFCU (see Durst et al 2003), the pressure changes in the pipe, induced by the turbulence structures during an intermittent transition process, did not affect the set mass-flow-rate value. Hence, the employment of the MFCU ensured constant Reynolds number operation of the test rig, in spite of the occurrence of the laminar-to-turbulent transition of the investigated pipe flows.…”

Section: D-2hmentioning

confidence: 99%

See 1 more Smart Citation

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Nishi¹,

Ünsal²,

Durst³

et al. 2008

J. Fluid Mech.

122

100

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Laminar-to-turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in the form of slugs. These are initiated by disturbances in the entrance region of a pipe flow, and grow in length in the axial direction as they move downstream. Sequences of slugs merge at some distance from the pipe inlet to finally form the state of fully developed turbulent pipe flow. This formation process is generally known, but the randomness in time of naturally occurring slug formation does not permit detailed study of slug flows. For this reason, a special test facility was developed and built for detailed investigation of deterministically generated slugs in pipe flows. It is also employed to generate the puff flows at lower Reynolds numbers. The results reveal a high degree of reproducibility with which the triggering device is able to produce puffs. With increasing Reynolds number, 'puff splitting' is observed and the split puffs develop into slugs. Thereafter, the laminar-to-turbulent transition occurs in the same way as found for slug flows. The ring-type obstacle height, h, required to trigger fully developed laminar flows to form first slugs or puffs is determined to show its dependence on the Reynolds number, Re = DU/ν (where D is the pipe diameter, U is the mean velocity in the axial direction and ν is the kinematic viscosity of the fluid). When correctly normalized, h + turns out to be independent of Re τ (where h + = hU τ /ν, Re τ = DU τ /ν and U τ = √ τ w /ρ; τ w is the wall shear stress and ρ is the density of the fluid).

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Section: Test Rig Triggering Device and Measurement Equipmentmentioning

confidence: 99%

Section: D-2hmentioning

confidence: 99%

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Nishi¹,

Ünsal²,

Durst³

et al. 2008

J. Fluid Mech.

122

100

View full text Add to dashboard Cite

show abstract

“…11. Figure 12 shows the ratio of the flow rates, q ta and q os , obtained from the h waveform by applying this procedure to the prescribed flow rates given by (1). Here, with regard to C d , Equation (8) is used for flows with Re ta ≥8000, and the empirical formula (3) [9] is used for flows with Re ta ≤8000.…”

Section: Procedures For Obtaining Pulsatile Flow Rate By Measuring Insmentioning

confidence: 99%

“…Moreover, the gas in an oxygenator and the blood in arteries are also unsteady and time-dependent periodic flows. Therefore, several studies have been carried out to obtain unsteady flow rates using conventional equipment [1][2][3]. Nevertheless, a number of problems remain to be solved [4].…”

Section: Introductionmentioning

confidence: 99%

Obtaining Pulsatile Flow Rate Using a 360-Degree Bend

Sumida¹

2015

ujme

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360-degree bend flowmeters were applied to determine pulsatile flow rates in water. Experiments were performed using bend flowmeters with curvature radius ratios of 7, 10 and 30 under the conditions of Womersley numbers of α=2.1−18, mean Reynolds numbers of Re ta =800−5×10 4 and oscillatory Reynolds numbers of Re os =600−1.6×10 4 . The pressure difference across the bend was found to be independent of the pulsation frequency and to conveniently vary with almost the same phase as the instantaneous flow rate. A method for measuring the instantaneous flow rate is proposed as well as a method for estimating the time-mean and amplitude values of the pulsatile flow rate. It is concluded that 360-degree bend flowmeters can be used to measure the pulsatile flow rate.

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“…Clearly, in these studies, substantial efforts must have been required in order to minimize the sensitivity dependence of density fluctuation on pressure and temperature variations. Durst et al [8] developed a mass flow rate controller using a valve and a laminar element that was designed to work up to unsteady oscillatory flow of 125Hz and showed experimental results up to 25Hz. Since the flow passed through a valve becomes a function of temperature, the accuracy could be improved if the temperature change is prevented.…”

Section: Introductionmentioning

confidence: 99%

Development of Unsteady Gas Flow Generator With Highly Precise Inlet Flow Rate Control System

Funaki¹,

Kato

Kawashima

et al. 2008

Proceedings of the JFPS International Symposium on Fluid Power

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In industry, an unsteady flow rate measurement of gases is becoming important increasingly. Our group has been developed an unsteady flow generator with an isothermal chamber for gases and showed that the calibration of the dynamic characteristics for the tested flow meter was effective. However, not only the measurement of the instantaneous flow rate value but also the evaluation of the time mean value in the unsteady flow becomes important in industry. And it was difficult to control precisely the time mean value of the generated flow rate using the former unsteady flow generator which we developed. In this research, to improve the precision of the generated flow rate with the unsteady flow generator, we suggest the inlet flow rate control method with the sonic nozzle and the high precise pressure control system and apply this method to the developed generator. Moreover, we perform the experiments and uncertainty analysis and confirm the effective of the suggested method.

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Mass flow rate control system for time-dependent laminar and turbulent flow investigations

Cited by 55 publications

References 8 publications

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Laminar-to-turbulent transition of pipe flows through puffs and slugs

Obtaining Pulsatile Flow Rate Using a 360-Degree Bend

Development of Unsteady Gas Flow Generator With Highly Precise Inlet Flow Rate Control System

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