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Importance of accurate fluid flow measurement in industry is crucial especially today with rising energy prices. There is no ideal measuring instrument due to numerous errors occurring during process of physical quantities measurement but also due to specific requirements certain instruments have like fluid type, installation requirements, measuring range etc. Each measuring instrument has its pros and cons represented in accuracy, repeatability, resolution, etc. Conventional single-hole orifice (SHO) flow meter is a very popular differential-pressure-based measuring instrument, but it has certain disadvantages that can be overcame by multi-holes orifice (MHO) flow meter. Having this in mind, the aim of this paper is to help gain more information about MHO flow meters. Both SHO and MHO gas (air) flow meters with same total orifice area and the pipe area ratio β were numerically studied and compared using computational fluid dynamics (CFD). Simulation results of 16 different orifices with four different β (0.5, 0.55, 0.6 and 0.7) were analysed through pressure drop and singular pressure loss coefficient. Standard k-ε turbulence model was used as a turbulence model. Beside singular pressure loss coefficient, pressure recovery as well as axial velocity for both the SHO and MHO were reported. Results showed lower (better) singular pressure loss coefficient and pressure drop as well as quicker pressure recovery in favour of the MHO flow meters. Also, centreline axial velocity results were lower for MHO compared to corresponding SHO. CFD simulation results were verified by experimental results where air was used as a working fluid. The influence of geometrical and flow parameters on singular pressure loss coefficient was also reported and results showed that MHO hole distribution did not have significant influence on singular pressure loss coefficient.

As the core pressure-regulating component of the Electronic Controlled Pneumatic Braking System (ECPBS) for commercial vehicles, the Automatic Pressure Regulating Valve (APRV) directly determines the accuracy and responsiveness of brake pressure adjustment, which is crucial for ensuring braking safety, stability, and ride comfort—especially in the context of autonomous driving. The pressure change rate is a key indicator reflecting braking smoothness and dynamic response performance, and its accurate calculation is the foundation for optimizing braking control strategies. To address the complexity and computational inefficiency in calculating the pressure change rate of multi-component, nonlinear APRV systems, this study proposes an equivalent calculation method based on throttle orifice flow characteristics. By equating the openings and chambers of an APRV to throttling orifices (fixed and variable) and variable-volume cavities, we simplified the complex pneumatic system while preserving its core dynamic characteristics. Theoretical derivation was conducted by integrating the first law of thermodynamics, ideal gas law, and flow equations for fixed/variable throttle orifices to establish a pressure change rate calculation model. The validity of the proposed method was verified through theoretical analysis, numerical simulation, and experimental testing. Compared with existing models, the proposed method achieved a balance between calculation accuracy and efficiency, with the simulation error within 2% (pressure) and 10% (pressure change rate), and it significantly improved computational efficiency compared to conventional models. This research provides a concise and accurate theoretical tool for the rapid prediction and precise control of pressure change rate in ECPBS, which is of great significance for optimizing autonomous driving braking planning, enhancing braking ride comfort by reducing vehicle jerk, and promoting the development of active safety technologies. The proposed equivalent modeling approach also offers a reference for the performance analysis of similar complex pneumatic components or systems.

A compact annular-radial-orifice flow magnetorheological (MR) valve with variable radial damping gaps was proposed, and its structure and working principle were also described. Firstly, a mathematical model of pressure drop was established as well to evaluate the dynamic performance of the proposed MR valve. Sequentially, the pressure drop distribution of the MR valve in each flow channel was simulated and analyzed based on the average magnetic flux densities and yield stress along the damping gaps through finite element method. Further, the experimental test rig was setup to explore the pressure drop performance and the response characteristic of the MR valve and to investigate dynamic performance of the valve controlled cylinder system under different radial damping gaps. The experimental results revealed that the pressure drop and response time of the MR valve augment significantly with the increase of applied current and decrease of the radial damping gap. In addition, the damping force of the proposed MR valve controlled cylinder system decrease with the increase of the radial damping gap. The maximum damping force can reach about 4.72 kN at the applied current of 2 A and the radial damping gap of 0.5 mm. Meanwhile, the minimum damping force can reach about 0.67 kN at the applied current of 0 A and the radial damping gap of 1.5 mm. This study clearly demonstrates that the radial damping gap of the MR valve is the key parameter which directly affects the dynamic characteristics of the valve controlled cylinder system, and the proposed MR valve can meet the requirements of different working conditions by changing the radial damping gaps.

【目的】利用大型渠道实测数据，评估不同弧形闸门过流公式的适用性和性能。【方法】以南水北调中线干渠严陵河闸为对象，收集约18 000组监测数据，分析不同工况下的闸孔出流特性，测试国内外常用的7种过流公式。【结果】实测闸下收缩断面弗氏数位于0.152~0.985区间，超出了南科院（NHRI）经验公式的适用范围；实测孔堰流分界点e/Hu接近0.991，超出了武水（WHUEE）经验公式的适用范围。CAP公式、无量纲公式和3种二次型经验系数公式的数据拟合R2分别为0.989、0.996、0.809、0.822和0.832，流量计算平均绝对误差MAE分别为2.25%、2.65%、4.11%、4.08%和3.98%。各公式在低、中潜流比下（Xr≤0.9）流量计算误差|E|max均小于10%，在高潜流比时（Xr＞0.9）达18%（CAP公式）、25%（无量纲公式）和36%左右（3种二次型经验系数公式）。【结论】所测大型弧形闸门的工作区间明显超出了南科院和武水经验公式的适用范围，5种国外公式在低、中潜流比下（Xr≤0.9）流量计算误差均在10%以内，在高潜流比下明显增大，推荐优先采用CAP公式和无量纲公式。

Extensive studies of the hydraulics of pipes have focused on limiting cases, such as fully-developed laminar or turbulent flow through long conduits and the accelerating flow through an orifice, for which there exist laws relating pressure drop and flow rate. We carry out experiments on smooth, circular pipes for dimensions and flow rates that interrogate intermediate conditions between the well-studied limits. Organizing this information in terms of dimensionless friction factor, Reynolds number and pipe aspect ratio yields a surface $f_D(Re,\\alpha )$ that is shown to match the three laws associated with developed laminar, developed turbulent, and orifice flows. While each law fails outside its applicable range of $(Re,\\alpha )$, we present a hybrid theoretical–empirical model that includes inlet, development and transition effects, and that proves accurate to approximately 10 % over wide ranges of $Re$ and $\\alpha$. We also present simple formulas for the boundaries between the three hydraulic regimes, which intersect at a triple point. Measurements show that sipping through a straw is an everyday example of such intermediate conditions not accounted for by existing laws but described accurately by our model. More generally, our findings provide formulas for predicting frictional resistance for intermediate-$Re$ flows through finite-length pipes.

This study investigates the performance of a newly designed high-porosity perforated-plate flow conditioner (HPPP) in improving flow measurement accuracy using orifice plates across a range of diameter ratios (β = 0.3–0.75). Experimental measurements were conducted to assess discharge coefficient deviations and axial velocity profiles downstream of the flow conditioners, with comparisons made against a standard Zanker conditioner and unconditioned flow. Results show that the HPPP conditioner consistently maintains discharge coefficient errors within the ±0.5% ISO 5167-2 tolerance for all tested β values, outperforming the Zanker design, particularly at low β where flow separation and sensitivity to disturbances are more pronounced. Velocity profile measurements further demonstrate the HPPP conditioner’s superior capability to restore flow symmetry and achieve a fully developed profile within a short downstream distance ( x / D ≈ 9), as opposed to x / D ≈ 13.5 for the Zanker. These findings confirm the HPPP conditioner as an efficient solution for enhancing orifice flow metering accuracy across a broad range of flow conditions.

This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally. Specifically, we report a quantitative form of the universal, cumulative energy distribution transferred to initially stationary sensor particles by quantum diffractive collisions. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined only by the analytic form of the interaction potential at long range. Using cold 87Rb sensor atoms confined in a magnetic trap, we observe experimentally p QDU 6 , the universal function specific to van der Waals collisions, and use it to realize a self-defining particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a fundamental advance for vacuum and pressure metrology. The quantum pressure standard realized here is compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N2. The pressure measurements agree at the 0.5% level.

This paper first uses a low-speed stereoscopic particle image velocimetry (SPIV) system to measure the convergent statistical quantities of the flow field and then simultaneously measure the time-resolved flow field and the wall mass transfer rate by a high-speed SPIV system and an electrochemical system, respectively. We measure the flow field and wall mass transfer rate under upstream pipe Reynolds numbers between 25 000 and 55 000 at three specific locations behind the orifice plate. Moreover, we apply proper orthogonal decomposition (POD), stochastic estimation and spectral analysis to study the properties of the flow field and the wall mass transfer rate. More importantly, we investigate the large-scale coherent structures’ effects on the wall mass transfer rate. The collapse of the wall mass transfer rates’ spectra by the corresponding time scales at the three specific positions of orifice flow suggest that the physics of low-frequency wall mass transfer rates are probably the same, although the flow fields away from the wall are quite different. Furthermore, the spectra of the velocity reconstructed by the most energetic eigenmodes agree well with the wall mass transfer rate in the low-frequency region, suggesting that the first several energetic eigenmodes capture the flow dynamics relevant to the low-frequency variation of the wall mass transfer. Stochastic estimation results of the velocity field associated with large wall mass transfer rate at all three specific locations further reveal that the most energetic coherent structures are correlated with the wall mass transfer rate.

Measurements of gas flow are crucial in medical applications like respiratory monitoring and mechanical ventilators. Variable area orifice Flow meters (VOFMs) are increasingly recognized for respiratory monitoring, functional assessment, and mechanical ventilation. Area variation of such a flowmeter can be achieved by setting a moving body inserted concentrically and guided through a central rod in the flowmeter, the mechanism that may affect the input-output relationship and produce bias error. Notwithstanding these problems, the VOFM has been advocated to utilize the feature of the membrane’s flexibility as a variable area orifice. Two flowmeter prototypes with flexible membranes the “Medical Flow Sensor FS2 by Hamilton” and the “Datex-Ohmeda Flow Sensor” are tested in this study. The former has a triangular orifice shape, while the latter is circular. A flow test rig is built enabling instantaneous measurements and recording of different air flow rates and differential pressure using a high-sensitivity differential pressure sensor. The experimental results are compared with the outcomes of the solved CFD model, which is solved using the FVM method. Results indicate that for a specified differential pressure (ΔP), the circular orifice sensor “Datex-Ohmeda Flow Sensor” consistently demonstrates a superior mass flow meter relative to the triangular sensor “Medical Flow Sensor FS2 by Hamilton.”

Accurate calculation of flow discharge for sluice gates is essential in irrigation, water supply, and structure safety. The measurement of discharge with the requirement of distinguishing flow regimes is not conducive to application. In this study, a novel approach that considers both free and submerged flow was proposed. The energy–momentum method was employed to derive the coefficient of discharge. Subsequently, the discharge coefficient was determined through the experiment which was performed on the physical model of a vertical sluice gate with a broad-crested weir. Feature engineering, incorporating dimensional analysis, feature construction, and correlation-based selection were performed. The best subset regression method was employed to develop regression equations of the discharge coefficient with the generated features. The derived formula was applied to compute the discharge coefficient in the vertical sluice gate and determine the flow discharge. The accuracy of adopted method was assessed by comparing it with recent studies on submerged flow, and the results demonstrate that the developed approach achieves a high level of accuracy in calculating flow discharge. The coefficient of determination for the calculated flow rate is 0.993, and the root mean square percentage error is 5.04%.