Noriyuki Furuichi

Friction factor and mean velocity profile for pipe flow at high Reynolds numbers

The friction factor for a fully developed pipe flow is examined at high Reynolds numbers up to ReD = 1.8 × 107 with high accuracy using the high Reynolds number actual flow facility “Hi-Reff” at AIST, NMIJ. The precise measurement of the friction factor is achieved by the highly accurate measurement of the flow rate, and the measurement uncertainty is estimated to be approximately 0.9% with a coverage factor of k = 2. The result examined here is obviously different from the Prandtl equation and the experimental results from the superpipe at Princeton University. The deviation of the present result from the Prandtl equation in the lower Reynolds number region is approximately 2.5% and −3% at the higher Reynolds number. For ReD 2.0 × 105, and it increases with the Reynolds number and reaches −6% at ReD = 1.0 × 107. The Karman constant estimated by the measured fric...

Multi-wave ultrasonic Doppler method for measuring high flow-rates using staggered pulse intervals

The ultrasonic pulsed Doppler method (UDM) can obtain a velocity profile along the path of an ultrasonic beam. However, the UDM measurement volume is relatively large and it is known that the measurement volume affects the measurement accuracy. In this study, the effect of the measurement volume on velocity and flow rate measurements is analytically and experimentally evaluated. The velocities measured using UDM are considered to be ensemble-averaged values over the measurement volume in order to analyze the velocity error due to the measurement volume, while the flow rates are calculated from the integration of the velocity profile across the pipe. The analytical results show that the channel width, i.e. the spatial resolution along the ultrasonic beam axis, rather than the ultrasonic beam diameter, strongly influences the flow rate measurement. To improve the accuracy of the flow rate, a novel method using a multi-wave ultrasonic transducer consisting of two piezo-electric elements with different basic frequencies is proposed to minimize the size of the measurement volume in the near-wall region of a pipe flow. The velocity profiles in the near-wall region are measured using an 8 MHz sensor with a small diameter, while those far from the transducer are measured using a hollow 2 MHz sensor in the multi-wave transducer. The applicability of the multi-wave transducer was experimentally investigated using the water flow-rate calibration facility at the National Institute of Advanced Industrial Science and Technology (AIST). As a result, the errors in the flow rate were found to be below −1%, while the multi-wave method is shown to be particularly effective for measuring higher flow rates in a large-diameter pipe.

A dealiasing method for use with ultrasonic pulsed Doppler in measuring velocity profiles and flow rates in pipes

The ultrasonic pulsed Doppler method (UDM) is a powerful tool for measuring velocity profiles in a pipe. However, the maximum detectable velocity is limited by the Nyquist sampling theorem. Furthermore, the maximum detectable velocity (also called Nyquist velocity), vmax, and the maximum measurable length are related and cannot be increased at the same time. If the velocity is greater than vmax, velocity aliasing occurs. Hence, the higher velocity that occurs with a larger pipe diameter, i.e. under higher flow rate conditions, cannot be measured with the conventional UDM. To overcome these limitations, dual-pulse repetition frequency (dual PRF) and feedback methods were employed in this study to measure velocity profiles in a pipe. The velocity distributions obtained with the feedback method were found to be more accurate than those obtained with the dual PRF method. However, misdetection of the Nyquist folding number using the feedback method was found to increase with the flow velocity. A feedback method with a moving average is proposed to improve the measurement accuracy. The method can accurately measure the velocity distributions at a velocity five times greater than the maximum velocity that can be measured with the conventional UDM. The measurement volume was found to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities using the dual PRF method. Integrating velocity distributions measured using the feedback method with a moving average makes it possible to accurately determine flow rates six times greater than those that can be determined using the conventional pulsed Doppler method.

Development of ultrasonic pulse-train Doppler method for velocity profile and flowrate measurement

We present a novel technique for measuring the velocity profile and flowrate in a pipe. This method, named the ultrasonic pulse-train Doppler method (UPTD), has the advantages of expanding the velocity range and setting the smaller measurement volume with low calculation and instrument costs in comparison with the conventional ultrasonic pulse Doppler method. The conventional method has limited measurement of the velocity range due to the Nyquist sampling theorem. In addition, previous reports indicate that a smaller measurement volume increases the accuracy of the measurement. In consideration of the application of the conventional method to actual flow fields, such as industrial facilities and power plants, the issues of velocity range and measurement volume are important. The UPTD algorithm, which exploits two pulses of ultrasound with a short interval and envelope detection, is proposed. Velocity profiles calculated by this algorithm were examined through simulations and excellent agreement was found in all cases. The influence of the signal-to-noise ratio (SNR) on the algorithm was also estimated. The result indicates that UPTD can measure velocity profiles with high accuracy, even under a small SNR. Experimental measurements were conducted and the results were evaluated at the national standard calibration facility of water flowrate in Japan. Every detected signal forms a set of two pulses and the enveloped line can be observed clearly. The results show that UPTD can measure the velocity profiles over the pipe diameter, even if the velocities exceed the measurable velocity range. The measured flowrates were under 0.6% and the standard deviations for all flowrate conditions were within ±0.38%, which is the uncertainty of the flowrate measurement estimated in the previous report. In conclusion, UPTD provides superior accuracy and expansion of the velocity range.

Further Investigation of Discharge Coefficient for PTC 6 Flow Nozzle in High Reynolds Number

The discharge coefficients of the throat tap flow nozzle based on ASME PTC 6 are measured in wide Reynolds number range from Red=5.8×104 to Red=1.4×107. The nominal discharge coefficient (the discharge coefficient without tap) is determined from the discharge coefficients measured for different tap diameters. The tap effects are correctly obtained by subtracting the nominal discharge coefficient from the discharge coefficient measured. Finally, by combing the nominal discharge coefficient and the tap effect determined in three flow regions, that is, laminar, transitional and turbulent flow region, the new equations of the discharge coefficient are proposed in three flow regions.Copyright

Experimental Results of Flow Nozzle Based on PTC 6 for High Reynolds Number

Discharge coefficients for three flow nozzles based on ASME PTC 6 are measured under many flow conditions at AIST, NMIJ and PTB. The uncertainty of the measurements is from 0.04% to 0.1% and the Reynolds number range is from 1.3×105 to 1.4×107. The discharge coefficients obtained by these experiments is not exactly consistent to one given by PTC 6 for all examined Reynolds number range. The discharge coefficient is influenced by the size of tap diameter even if at the lower Reynolds number region. Experimental results for the tap of 5 mm and 6 mm diameter do not satisfy the requirements based on the validation procedures and the criteria given by PTC 6. The limit of the size of tap diameter determined in PTC 6 is inconsistent with the validation check procedures of the calibration result. An enhanced methodology including the term of the tap diameter is recommended. Otherwise, it is recommended that the calibration test should be performed at as high Reynolds number as possible and the size of tap diameter is desirable to be as small as possible to obtain the discharge coefficient with high accuracy.Copyright

Application of a novel method for validating the uncertainty estimation of a flow test facility

Abstract After a large heat meter flow test rig was overhauled, making a thorough characterization and re-validation of the associated uncertainty is necessary. Validating the uncertainty through interlaboratory comparisons takes years and is not always successful. Therefore, a method is proposed to validate the uncertainty estimation based on a flow meter Reynolds number similarity in between comparisons. The newly estimated uncertainty of an overhauled facility is schematized and the proposed method is applied. The obtained results are confirmed through a conventional international interlaboratory comparison.

Effect of low-frequency ultrasound on flow rate measurements using the ultrasonic velocity profile method

This study presents a low-frequency ultrasonic propagation analysis using the finite-element method (FEM). Experimental results of flow rate measurements using the ultrasonic velocity profile (UVP) method are also presented. The ultrasound frequency, pipe diameter, and pipe wall thickness are 0.274 MHz, 590.6 mm, and 9.5 mm, respectively. Six waves are generated per ultrasound pulse. To analyze the entire pipe region, the FEM is combined with the Kirchhoff method. The experiments of flow rate measurements are conducted using the high Reynolds number calibration facility at the National Metrology Institute of Japan. The range of the Reynolds number is from 4.4×106 to 1.7×107. Wide spreading of the ultrasonic beam in the axial direction of the pipe is observed because of multiple reflections in the pipe wall. This wide beam affects the measured velocity profile, particularly in the region near the pipe wall. In addition, the flow rate errors are approximately 10% (deviating by 1.1%) across the investigated range of Reynolds number. This result suggests that the experimental flow rate errors might be used as correction factors of flow rate measurements using the UVP method.

Measurement of Fluid Flow

On the basic of the ultrasonic principle made clear in Chaps. 1– flow velocity profiling can be realized if the Doppler method is applicable to the flow system. There are standard velocity fields, which are the most appropriate systems for examining the performance of ultrasonic velocity profiling (UVP) and training users in making UVP measurements. The standard velocity fields have a one-dimensional one-component velocity distribution, irrespective of whether they are steady or unsteady, such as in the case of flow in a rotating circular cylinder and laminar flow in a pipe. Measuring flow in such systems helps clarify the functions of UVP subject to diverse practical problems. Once velocity information is acquired, it is suitably adjusted in post-processing. Post-processing has two purposes: one is to improve the data quality in response to the inclusion of noise in velocity data, and the other is to derive statistical and other quantities.

Uncertainty Examination of New Water Flow Calibration Facility for Nuclear Power Application

A new test facility has been constructed at National Metrology Institute of Japan (NMIJ) for calibration of feed water flowmeters at nuclear power stations for Reynolds numbers of up to 16 million. This very large Reynolds number is achieved at a flow rate of 3.33 m3 /s (12,000 m3 /h) and water temperature of 70 degrees C in a 600 mm pipe. This new facility has four sets of pumps and reference flowmeters installed in parallel upstream of the test section. These flowmeters are calibrated at 0.83 m3 /s (3,000 m3 /h) one by one without dismounting from the loop by using a 50 t weighing tank; this tank has been used as the primary standard for the existing flow facility. Then the flow rate can be increased up to 3.33 m3 /s (12,000 m3 /h) with all of the pumps and flowmeters working at the same time. This paper describes the concept of the new facility, the fundamental uncertainty estimation, and the examination of its measurement capability.Copyright