The capability to calibrate flow and volume devices dynamically has gained increasing interest over the years. Within the scope of the EMPIR project 17IND13 ‘Metrology for real-world domestic water metering’, several test rigs were developed with which dynamic flow profiles can be generated and measured that reflect characteristics of real-world drinking water consumption. The dynamic component of the test rigs is realized based on different technologies such as valves, cavitation nozzles or piston provers. For validation purposes, an intercomparison of the test rigs was carried out in the scope of an EURAMET pilot study no. 1506. Between September 2020 and February 2021, a transfer standard specially developed for the intercomparison was calibrated at eight laboratories. The measurement error was determined for three dynamic flow profiles representative of drinking water consumption in Europe. In addition to determining the measurement errors and the degree of equivalence, five additional key parameters were derived to characterize the test rig properties: (1) repeatability of the profile measurements, (2) mean value of the residuals, (3) deviation between measured total mass and total mass resulting from the given profile and (4) duration of the flow change for an increasing change (5) and duration of the flow change for a decreasing change. These key parameters comprehensively describe the quality with which the dynamic flow profiles were generated and measured on the test rigs and can be used for evaluations in future intercomparisons of this kind. A main outcome of the intercomparison is that there is no technology to be preferred in terms of technical implementation. All test rigs agree well with each other, taking into account their expanded measurement uncertainties.

Water meters of different types and sizes are used to monitor and bill the water supply. Although the water is of drinking water quality, its chemo-physical properties often enough adversely affect the measuring behaviour of a meter after a while. There is thus the risk that they no longer meet the legal requirements and may no longer be used. In this paper a test regime with a focus on pH, total hardness and particle load is presented which allows water meters to be tested closer to their operating conditions prior to placing them on the market. The regime goes beyond the conventional continuous durability test as described in OIML R49:2013(E) and ISO 4064:2014. The feasibility and reliability of the test regime has been demonstrated through implementation at different facilities. In the study, the measurement performance of water meters of various types and from different manufacturers was also investigated. A heterogeneous spread of measurement errors was found for both, water meters in mint conditions and those which were exposed to a defined water quality. Furthermore, compared to the conventional continuous durability test, the test regime developed in the study generally leads to stronger changes in the measurement error of the water meters.

The reduction of water consumption and the technical developments of the last decades, such as the use of tap aerators, water-saving appliances or the use of electronic measuring principles for water consumption measurements at household level, lead to increased and novel demands on flow metering technology. Nowadays, the meters used must be able to detect less water volume with a constant meter size and constantly changing flows. This makes it necessary. to check whether the demanded measurement accuracy is maintained under these changed boundary conditions. Against this background, the question arises to what extent the existing test regimes to assess the measuring performance of water meters are still appropriate. In order to answer this question, it is necessary to set up a metrological infrastructure that will enable water meters to be tested close to real-world operation conditions. Therefore, the following paper focusses on flow dynamics within the water consumption at the household level. One key factor to realize a representative test regime are reliable and representative water consumption measurements at household level. Within the "Metrology for real-world domestic water metering" project (MetroWaMet) within the European Metrology Programme for Innovation and Research (EMPIR) water consumption measurements were carried out in different European countries. Based on the water consumption measurements discussed essential consumption characteristics can be derived in terms of amplitudes and amplitude distributions, gradients or durations. One important outcome of the study is that water consumption in the four different European countries is comparable. This means based on the available consumption data a generally applicable test regime can be derived which can be extended if necessary. The guide developed regarding the planning and carrying out of consumption measurements can be used to collect further reliable and representative consumption data.

Recent studies on laminar, fully-developed, sinusoidally pulsating pipe flows have revealed the existence of a unique signature map that can be used for the measurement of the arbitrary time-varying, instantaneous mass flow rate from the recorded axial pressure gradient data and vice versa. This measuring technique is, however, valid for the hydrodynamically fully-developed flow of an incompressible fluid. The present study, therefore, deals with the numerical evaluation of the required development length as functions of the mean Reynolds number, the amplitude of mass flow rate pulsation and the pulsation frequency in the moderate and high Reynolds number regimes. The investigation shows that in the low-frequency, quasi-steady regime, the instantaneous variations of L/D can be predicted by the steady-state results for corresponding instantaneous Reynolds numbers. On the other hand, at higher pulsation frequencies, considerable deviation from the pure sinusoidal signal occurs for the development length and its amplitude decreases with increase in pulsation frequency. Finally, using the results of the present simulations, a simple correlation is proposed that can be used in order to predict the maximum development during a cycle as functions of Re-M, (m) over dot(A)* and F. (C) 2012 Elsevier Inc. All rights reserved.

FMP Technology GmbH has developed a new injection valve for internal combustion engines with a modification of the fuel guidance. The valve does not exhibit the high pressure fluctuations that generally occur in the supply lines, and the entire fuel injection system works virtually without pressure waves. Due to this new method of fuel guidance, the fuel is no longer accelerated or decelerated when the valves open and close. Instead, the fuel is diverted. Because of this, the major part of the fuel in the supply lines does not change its state of motion when the valve is opened and closed. With the proposed valve, the injected mass of the fuel can be determined simply by the duration of the opening time. This is shown by numerous numerical studies carried out by the authors. Experimental verifications still need to be performed.

Die FMP Technology GmbH entwickelt ein neuartiges Einspritzventil für Verbrennungsmotoren mit einer geänderten Kraftstoffführung. Dieses Ventil zeigt nicht die üblicherweise in den Kraftstoffzuleitungen auftretenden hohen Druckpulsationen; das gesamte Einspritzsystem arbeitet praktisch druckwellenfrei. Dies bringt beachtliche Vorteile bezüglich der Kontrolle des Einspritzvorganges mit sich, da druckwellenbedingte Schwankungen der eingespritzten Kraftstoffmenge nicht mehr auftreten. Durch die neue Weise der Kraftstoffführung wird die bei Ventilöffnung und -Schließung zugeführte Kraftstoffmenge nicht mehr beschleunigt oder abgebremst. Stattdessen wird der Kraftstoff umgelenkt. Dadurch ändert der größte Teil des Kraftstoffes, im Ventil und in den Zuleitungen, seinen Bewegungszustand beim Öffnen und Schließen des Ventils nicht. Mit Ventilen dieser Art lässt sich die eingespritzte Kraftstoffmenge allein über die Öffnungszeiten des Ventils bestimmen. Dies zeigen umfassend numerische Berechnungen. Experimentelle Verifikationen stehen noch aus.

Hot-wire anemometry is a measuring technique that is widely employed in fluid mechanics research to study the velocity fields of gas flows. It is general practice to calibrate hot-wire sensors against velocity. Calibrations are usually carried out under atmospheric pressure conditions and these suggest that the wire is sensitive to the instantaneous local volume flow rate. It is pointed out, however, that hot wires are sensitive to the instantaneous local mass flow rate and, of course, also to the gas heat conductivity. To calibrate hot wires with respect to mass flow rates per unit area, i.e., with respect to (ρU), requires special calibration test rigs. Such a device is described and its application is summarized within the (ρU) range 0.1–25 kg/m2 s. Calibrations are shown to yield the same hot-wire response curves for density variations in the range 1–7 kg/m3. The application of the calibrated wires to measure pulsating mass flows is demonstrated, and suggestions are made for carrying out extensive calibrations to yield the (ρU) wire response as a basis for advanced fluid mechanics research on (ρU) data in density-varying flows.

Laminar-to-Turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in form of slugs. These form as intermittent disturbances in the entrance region of a pipe, grows in axial direction as they move downstream and join at some distance of the pipe inlet. In this way, the fully development of turbulent flow is formed in the far downstream region. This is shown in the paper and the merging of slugs from the entrance to the exit of pipe flows is quantified. A special flow test rig was developed and built for the described investigations and was employed for detailed investigations of laminar-to-turbulent transition studies. The paper also describes the triggered transition at relatively lower Reynolds numbers yielding the transition of puffs. They form by the introduced disturbances and developed afterwards into slugs with a higher front than back edge velocity. Thereafter the flow development occurs as found for slug flows.

A method of measuring the instantaneous mass flowrates of fuels passing through fast operating injection nozzles is described. The flowrate information is deduced from instantaneous pressure gradient measurements. Through a Fourier transformation, the Fourier coefficients of the pressure gradient are determined, which are used for the calculation of the transient mass flowrate of fuel through injection nozzles, utilizing a special reconstruction algorithm. The theoretical background of the measurement method is provided and the development work to yield a practically applicable measuring system is summarized. The latter is used for verification experiments, providing time-resolved flowrates for a magnetically driven injection valve operating at a pressure of approximately 6 bar. Online measurement of the injection mass flowrates can be recorded with this measuring system and information can be obtained for individual injection events. Cycle-to-cycle variations can be detected in this way.

Combined analytical and experimental investigation of sinusoidal mass flow-controlled, pulsating, laminar and fully developed pipe flow was carried out. The experimental investigation employed a mass flow control unit built at LSTM-Erlangen for the present investigation. For the analytical investigation, the equations describing such flows were normalized to allow for a general solution, depending only on the normalized amplitude mA* of the mass flow pulsation and the normalized frequency F. The analytical and experimental results are presented in this normalized way and it is shown that good agreement between the results of the authors is obtained. A diagram is presented for the condition of flow reversal in terms of the dimensionless frequency F and the mass flow rate amplitude mA*.

In the present paper a method to measure the instantaneous mass flow rates of fuel passing through fast operating injection nozzles is described. The flow rate information is deduced from instantaneous pressure gradient measurements. Through a Fourier transformation Fourier-coefficients of the pressure gradient are determined, which are used for the calculation of the transient mass flow rate of fuel through injection nozzles, utilizing a special reconstruction algorithm. In the paper the theoretical background of the measuring method is provided and the entire development work is summarized as car-ried out by the authors to yield a practically applicable measuring system. The latter is used for verification experiments providing time resolved flow rates for a magnetically driven injection valve operating at a pressure of approximately 6 bars. The authors stress that on-line measurements of the injection mass flow rates can be presented with their developed measuring system.

The authors’ research work into fully developed pulsating and oscillating laminar pipe and channel flows raised questions regarding the development length of the corresponding steady flow. For this development length, i.e., the distance from the entrance of the pipe to the axial position where the flow reaches the parabolic velocity profile of the Hagen-Poiseuille flow, a wide range of contradictory data exists. This is shown through a short review of the existing literature. Superimposed diffusion and convection, together with order of magnitude considerations, suggest that the normalized development length can be expressed as L∕D=C0+C1Re and for Re→0 one obtains C0=0.619, whereas for Re→∞ one obtains C1=0.0567. This relationship is given only once in the literature and it is presumed to be valid for all Reynolds numbers. Numerical studies show that it is only valid for Re→0 and Re→∞. The development length of laminar, plane channel flow was also investigated. The authors obtained similar results to those for the pipe flow: L∕D=C0′+C1′; Re, where C0′=0.631 and C1′=0.044. Finally, correlations are given to express L∕D analytically for the entire Re range for both laminar pipe and channel flows.

Investigations of time-dependent laminar and transitional flows need accurate and reproducible generation of the flow as a function of time. For this purpose, an electronically controlled air valve, with which the mass flow rate is controlled, was designed and built. The working principle and lay-out of the valve are explained and the performance of the valve is demonstrated. It was found that with the present equipment one can study any nonperiodic and periodic flow and the flow can be adjusted to be laminar, transitional and turbulent. The investigations on laminar and transitional time-dependent flows are reported. Laminar flow investigations showed that the generated sinusoidal mass flow rates agree well with that of analytical solution. Non-periodic transient and periodic sinusoidal pulsatile transitional flows were investigated. It was shown that elucidation of the transition in non-periodic transient flows may help in understanding the transition in periodic flows.

Pressure gradient driven, laminar, fully developed pulsating pipe flows have been extensively studied by various researchers and the data for the resultant flow field are available in a number of publications. The present paper, however, concentrates on related flows that are mass flow driven, i.e., the flows where the mass flow rate is prescribed as m=mM+mAfm(t) and fm(t) is periodically varying in time. Sinusoidal and triangular mass flow rate pulsations in time are analytically considered in detail. Results of experimental investigations are presented and are complemented by data deduced from corresponding analytical and numerical studies. Overall, the results provide a clear insight into mass flow rate driven, laminar, fully developed pulsating pipe flow. To the best of the authors’ knowledge, flows of this kind have not been studied before experimentally, analytically and numerically.

Most experimental flow investigations are carried out under imposed steady-state flow conditions. The major reason for this is that there is a lack of experimental facilities to impose well-controlled time-dependent inlet and outlet conditions on flows. There is apparently no equipment available to supply, in a well-controlled manner, the mass flow rate for time-dependent internal flow investigations. The work described in this paper remedies this situation. It introduces the basic ideas for a mass flow rate control system for time-dependent laminar and turbulent flow investigations. A first unit was built for controlled mass flow rate variations in the range of 0–217.8 g min−1 under atmospheric conditions corresponding to 0–180 l min−1. With this first unit the authors demonstrate that the basic ideas put forward in the paper can be used to build mass flow rate control units for experimental fluid mechanics studies. The flow rate can be simply controlled by a voltage input. The system was designed to work up to frequencies of 125 Hz.