Orifice Opening Research Articles

Experimental Investigation of Effect of Orifice Diameter on Volumetric Efficiency of Two-Stage Reciprocating Air Compressor

The volumetric efficiency is an important parameter commonly adopted to quantify the performance of air compressors. The present work is concerned with the design of an optimum air intake system for a single acting two stage reciprocating air compressor. The intake air system comprised of different diameter of orifice which affect the quantity, pressure of air to the compressor. The study approaches the effect of change in the intake orifice opening, affects the volumetric efficiency of air compressor. In this we used the standard procedure to find the efficiency, and it shows us the as orifice diameter increases the volumetric efficiency changes with increasing order to some extent

Predicting discharge coefficient of weir–orifice in closed conduit using a neuro-fuzzy model improved by multi-phase PSOGSA

This study investigates the viability of a strong algorithm (PSOGSA) merging particle swarm optimization (PSO) and gravity search algorithm (GSA) in tuning adaptive neuro-fuzzy system (ANFIS) parameters for modeling dimensionless experimental discharge of combined weir–orifices. The results are compared with the standard ANFIS and two hybrid models ANFIS tuned with PSO and GSA. The models are assessed by applying several dimensionless input parameters, consisting h/D (the ratio of upstream water depth to channel diameter), W/D (the ratio of orifice opening height to channel diameter), H/D (the ratio of plate height to channel diameter) and using comparison indices such as root-mean-square error and mean absolute error. The outcomes reveal that the new ANFIS-PSOGSA method provides superior accuracy in modeling dimensionless experimental discharge over the ANFIS-PSO, ANFIS-GSA and standard ANFIS method. Among the input parameters, the h/D was found to be the most effective input on modeling dimensionless experimental discharge while involving the H/D parameter deteriorated the models’ performances. The relative root-mean-square error differences between ANFIS-PSOGSA and ANFIS are found as 50% and 68.29% for pipe A and B, respectively. By implementing the ANFIS-PSOGSA, the accuracy of ANFIS-PSO and ANFIS-GSA is also improved in modeling dimensionless experimental discharge by 45.71% and 29.63% in pipe A and by 63.89% and 45.83% in pipe B with respect to root-mean-square error.

Propulsive characteristics of single-pulsed jets with tube and orifice openings

The effects of the nozzle exit geometry on the unsteady propulsive characteristics of single-pulsed jets are studied numerically. For both tube and orifice nozzles, the jet exit configuration is parameterized by the diameter ratio RD, which is defined as the ratio of the nozzle entrance D0 to the jet exit diameters D. It is found that the diameter ratio has significant influence on the propulsive characteristics of the single-pulsed jet during its entire ejection phase. The total impulse production is augmented considerably as the diameter ratio increases until a critical value of RD_cir≈2.0 is approached. The larger impulse production by the orifice nozzles over the tube nozzle stems from the persistent over-pressure contribution at the jet exit due largely to the fact that the flow contraction near the jet exit of the orifice nozzle results in the intensification of the radial velocity gradients and higher local pressure. By using the existing prediction of the contraction coefficient Cc to account for the flow contraction, a theoretical model has been developed with the quasi-one-dimensional flow approximation to predict the pressure thrust at the jet exit during the steady discharging stage, showing good agreement with the present numerical results. Moreover, the pressure force acting on the vertical wall of the orifice nozzle, which is proportional to the wall area, is found to be primarily responsible for the larger transient variations in the jet impulse during the onset and end of the jet ejection phase as the diameter ratio increases.

The effect of rotational speed on force and torque during instrumentation of simulated root canals using ProTaper Next rotary files

Introduction: Rotary nickel–titanium files are subjected to shear and flexural stresses during instrumentation. Increasing the rotational speed may reduce the shear stresses but can deteriorate the fatigue life of the file. This in vitro study aimed to address the influence of three rotational speeds 300, 500, and 700 RPM on the apical force and torque generated during instrumentation as well as on file fracture. Materials and Methods: A total of 48 simulated canals were divided into three groups: 300, 500, and 700 RPM (n = 16). Each canal was instrumented using a ProTaper Next XA orifice opener to prepare the coronal third and an X2 shaper to prepare the middle and apical thirds. A new set of files (XA and X2) was used to prepare four canals. A customized setup was used to evaluate the maximum apical force and torque corresponding to each third of the canal. The files were inspected for deformation or fracture using a stereomicroscope. Force and torque data were analyzed using analysis of variance and Post hoc Tukey test at 5% significance. Results: Five hundred and 700 RPM generated a significantly lower apical force and torque than 300 RPM at all canal thirds (P < 0.001). However, 700 RPM was superior to 500 RPM at the coronal third only (P < 0.001). No incidence of deformation or fracture was reported in any group. Conclusions: In resin artificial canals, increasing the rotational speed of the tested ProTaper Next files resulted in significantly less apical force and torque without increasing the incidence of fracture. Further studies involving natural teeth are required to validate these results using natural teeth.

Enhancing wave energy harvesting: Performance analysis of a dual chamber oscillating water column

This study investigates the hydrodynamic characteristics of a dual chamber oscillating water column (OWC) setup through a series of experiments, aiming to assess its potential for harvesting wave energy. The investigation involves varying frontwall drafts, power take-off (PTO) dampings, and incident wave conditions, while quantitatively evaluating the OWC system's performance using the capture width ratio (CWR) as the key metric. The findings indicate that the dual chamber configuration consistently exhibits enhanced performance for all combinations of orifice ratios, opening heights, and incident wave frequencies studied. As expected, increasing the opening height of the second chamber leads to improved performance of the OWC. Interestingly, the effect of varying applied PTO damping on improvement of CWR values is found to be relatively insensitive. The most significant improvements in CWR are observed for larger incident wave frequency values. For instance, for dimensionless wave frequency (Kh) values of 1.43 and 1.68, the CWR increases from 0.47 and 0.26 to 0.72 and 0.52, respectively, with the orifice ratio combination of τ1, 0.015, and τ2, 0.018. It is worth noting that the single chamber OWC operates most efficiently within the resonant frequency range of 0.94–1.23, while the dual chamber design extends this frequency range, enabling efficient wave energy capture over a wider spectrum of wave conditions. The dual chamber configuration offers considerable advantages for wave energy conversion applications by increasing the effective frequency bandwidth for optimal energy capture. The research findings suggest that this innovative design has the potential to significantly enhance the efficiency and adaptability of wave energy converters, contributing to the advancement of sustainable and renewable energy technologies.

Numerical investigation on the hydrodynamic performance of a land-based OWC system with multi-chamber modules

Modular design of wave energy converters (WECs) can offer a promising scheme to improve the economic competitiveness of wave energy by reducing the levelized cost of energy. In this study, the hydrodynamic performance of a land-based oscillating water column (OWC) system with multi-chamber modules is evaluated to optimize the layout and design of the system, the OWC structure is extended to five-chamber modules. A two-dimensional wave flume is developed using the high-order boundary element method to simulate the interaction of the incident waves with the OWC device based on the fully non-linear potential flow theory. The proposed numerical model is validated by published experimental data. It is concluded that the two-chamber installation provides superior hydrodynamic performance compared with the single-chamber OWC. The five-chamber OWC system is more suitable for energy capture in low-frequency wave conditions, where the first and last chambers are dominant in energy extraction. From the perspective of energy conversion efficiency and economy, the two- and three-chamber systems are most suitable for targeting low and high frequency waves in the tested conditions, respectively. Additionally, the resonant frequency of the single-chamber module plays a decisive role in the energy capture of the OWC system, and a chamber with a low resonant frequency and a small orifice opening ratio should be selected as the module unit. This paper provides valuable guidance for the modular application of OWCs and the arrangement of multiple chambers.

Experimental comparison of the upstream head using the non-rotating model of the vertical ultra-low head hydro turbine with its prototype

A vertical ultra-low head (VULH) turbine is a pico-scale hydro turbine applicable to open canal flow with or without head drop. This conceptualized turbine rotates at a lower speed. In the case of water flow on a canal without head drop condition, the prediction of the upstream head is challenging due to the change in the direction of the water flow path on this conceptualized system. Assuming the head at the primary level of design, an experimental study has been conducted to judge the upstream head of water flow using the two-dimensional non-rotating model (NRM) before the use of a prototype of the turbine. The runner was designed with a conventional method whereas the design of NRM was based on the diameters of the runner designed and the orifice openings on it. The experiments were conducted on a newly developed VULH Turbine test rig of size 10 m x 1.5 m x 2 m with a maximum flow rate capacity of 120 LPS and a maximum upstream head of 0.75 m. The tests were completed for upstream head variation using three different sets of NRM having an orifice cut angle of 15°, 18°, and 22.5° and a prototype of the runner at a constant speed for different flow rates. From the comparisons made, the closest NRM was selected that showed a similar upstream head at the maximum efficiency point of the runner. The research concluded with the finding that the NRM can be used to predict the upstream head of the VULH turbine instead of the rotating model.

Pretreatment of Landfill Leachate Using Hydrodynamic Cavitation at Basic pH Condition

The leachate generated from a landfill can cause significant harm to the environment and human health, so it must be treated before being discharged. A biochemical method is effective to treat the landfill leachate, but it requires a physicochemical pretreatment to help reduce the organic load and improve the biodegradability of the landfill leachate. In this work, hydrodynamic cavitation was used to pretreat the landfill leachate due to it being cost-effective, without additional chemicals, and environmentally friendly. The pretreatment experiments were conducted under an inlet pressure of 0.4 MPa and a basic pH. The influence of operating parameters such as the orifice opening rate, the arrangement of orifices, and the reaction time on the chemical oxygen demand, ammonium nitrogen, and biochemical oxygen demand removal in landfill leachate was studied, and the energy efficiency was evaluated. The results showed that under the above conditions, the removal rate for the chemical oxygen demand of the orifice plate with an annular orifice arrangement was better than that of the orifice plate with a radiation orifice arrangement, and the orifice plate with an orifice opening rate of 0.0417 had the best effectiveness. The energy efficiency under these two optimization conditions was also the highest. When the optimal operation time was 60 min, the removal rate of the chemical oxygen demand was 22.63%. The biodegradability of the landfill leachate was significantly improved with BOD5/COD increasing by 57.27%. The study provides a theoretical basis and data support for the application of hydrodynamic cavitation as a low-cost and efficient treatment method in the pretreatment of landfill leachate.

Computational Simulation of the Flow Induced by Water Leaks in Pipes

Despite recent advances in leak detection in water supply systems, previous studies focused mainly on material aspects or orifice opening characteristics. This study evaluated geometric, hydraulic, and hydrodynamic factors influencing on water leaks using three-dimensional (3D) computational fluid dynamics (CFD) simulations. The simulated discharge coefficient (Cd) had a maximum absolute deviation of 8% compared with experimental data. The results indicated that the variation of Cd as a function of the diameter and orifice size can be attributed to the effect of tube curvature on flow convergence through the orifice. The statistical analysis concluded that the orifice-to-pipe diameter ratio d/D is the best dimensionless parameter that explains this phenomenon, which agreed with the analyses of the streamlines and turbulent eddy dissipation rate in the simulations. Other important dimensionless parameter are the ratio of the pressure head differential at the orifice to the pipe diameter ΔH/D, Reynolds number (R), and the ratio of the pressure head differential at the orifice to the wall thickness ΔH/e, in order of relevance. A set of empirical correlations was elaborated through a nonlinear multiple regression analysis with Reynolds numbers ranging between 12,000 and 52,000, and pressure head differential ranging from 1 to 45 m. This study advances the knowledge of cross-flows through orifices, and the proposed correlations potentially can improve the prediction of water leaks in pipes.

Challenges in diagnosing vaginal mass in a pregnant woman with an underlying duplex collecting system disease: a case report.

In this case, a 23-year-old pregnant woman at 32 weeks came to the clinic for a routine check-up. A vaginal mass had been noticed during the examination and was punctured, revealing unknown fluid. Further investigations revealed left duplex collecting system consisted of an upper moiety opening with a ureterocele in the anterior wall of the vagina and a lower moiety ending with an ectopic orifice near the right ureter orifice. Therefore, the modified Lich-Gregoir procedure was done to reimplant the ureter of the upper renal moiety. Postoperative following-up investigations affirmed improvement without complications. The duplex collecting system disease may remain asymptomatic until adulthood or present with unexpected symptoms. The subsequent workup in the duplex kidney disease depends on the moieties' function and the ureter orifice opening site. Although the Weigert-Meyer rule is usually used to describe the typical pattern of duplex collecting system ureters opening sites, it has many expectations in the literature. This case shows how some common symptoms may lead to finding an unexpected urinary tract abnormality.

New computational approach to shunt design in congenital heart palliation

Shunts are commonly used to redirect blood to pulmonary arteries in procedures that palliate congenital cardiovascular defects. Previous clinical studies and hemodynamic simulations reveal a critical role of shunt diameter in balancing flow to pulmonary versus systemic vessels, but the biomechanical process of creating the requisite anastomosis between the shunt and host vessel has received little attention. Here, we report a new Lagrange multiplier-based finite element approach that represents the shunt and host vessels as individual structures and predicts the anastomosis geometry and attachment force that result when the shunt is sutured at an incision in the host, followed by pressurization. Simulations suggest that anastomosis orifice opening increases markedly with increasing length of the host incision and moderately with increasing blood pressure. The host artery is further predicted to conform to common stiff synthetic shunts, whereas more compliant umbilical vessel shunts should conform to the host, with orifice area transitioning between these two extremes via a Hill-type function of shunt stiffness. Moreover, a direct relationship is expected between attachment forces and shunt stiffness. This new computational approach promises to aid in surgical planning for diverse vascular shunts by predicting in vivo pressurized geometries.

Evaluation of Surface Skimmer Flow Rates and Size Selection

A floating surface skimmer is a device used to dewater a sediment basin as it fills. The skimmer floats on the surface, draining the least turbid water as sediment falls out of suspension. An adjustable orifice on the skimmer regulates the filling and draining rate of the basin. After significant runoff events, skimmers slowly drain the basin over several days to maximize settling, while draining less turbid water from the top of the water column. Manufacturers have published data for products that customers can use to decide on the skimmer type, size, and orifice opening, but these design parameters tend to be very rough estimates with numerous assumptions. This study details a methodology for testing skimmers, including the materials, data collection process, and data analysis approach required to obtain the most accurate skimmer flow rate data. Testing was performed on a 15.2 cm (6.0 in.) post-construction stormwater skimmer prototype provided by J.W. Faircloth & Son, Inc., in an approximately 30 m3 (1000 ft3) evaluation tank. This skimmer used an adjustable sluice gate to control flow rate and had two barrel lengths. Six sluice gate opening sizes were tested three times for both barrel lengths, resulting in 36 tests performed. Experiments revealed that the skimmer had a capacity ranging from 0.03 m3/s (0.5 ft3/s) with a 2.54 cm (1.0 in.) opening and a capacity of 0.071 to 0.085 m3/s (2.5–3.0 ft3/s) with an opening of 15.2 cm (6.0 in.). Experimental results were then used to create a user-interactive skimmer sizing tool to provide more accurate information on sediment basin storage and drawdown times based on skimmer selection.

Experimental investigation on flow approach profile for comparison of surface velocity at the inlet of the vertical ultra-low head hydro turbine using a non-rotating model

This article reports the need for an inlet approach profile in front of the turbine system for the newly developed vertical ultra-low head turbine applicable on channel flow section without dropped bed level. The fixed wall available in the conceptualization stage was found to act as a barrier to a certain level disturbing the flow towards the turbine that need to rectify with the addition of a suitable profile. The four-simple geometry for inlet approach profiles as vertical, inclined, curved, and a combination of inclined and curved profiles were selected for testing in pair with the alternation of a two-dimensional non-rotating model of the turbine having 150, 180, and 22.50 orifice opening on it. With the review of the literature, a different experimental methodology has been explained. The tests were conducted on an experimental setup tank of the length of 10 m developed for the vertical ultra-low head hydro turbine with input variables such as flow rate, inlet profile, and non-rotating models. The experimental analysis is presented about the vertical profile with the concern of flow surface velocity and upstream height possessed by different combinations. The comparisons made for upstream height and surface velocity with different flow rates, upstream height with surface velocity, maximum surface velocity, and upstream height with orifice opening of non-rotating models are discussed and selected the most suitable one among the tested. The conclusion is made for the necessity of an inlet approach profile with suitable geometry to minimize the loss at turbine inlet mentioning the future task is desired for optimization.

Interventional treatment and early-stage follow-up of pulmonary atresia with intact ventricular septum

Objective: To explore the application value of percutaneous peripheral interventional therapy in pulmonary atresia with intact ventricular septal (PA-IVS). Methods: Retrospective case summary. The data was collected from 25 children who were hospitalized at the Children's Hospital,Zhejiang University School of Medicine from August 2019 to August 2022, had been diagnosed with PA-IVS by echocardiography, and underwent interventional treatment. The sex, age, weight, operation time, radiation exposure time, and radiation dose of the patients were collected. The patients were divided into the arterial duct stenting group and the non-stenting group. Preoperative tricuspid annular diameters and Z scores, right ventricular length diameters, and right ventricular/left ventricular length-diameter ratios were compared by paired t-tests. Right ventricular systolic pressure difference, oxygen saturation, lactic acid before and after the surgery were compared for 24 children who received percutaneous balloon pulmonary valvuloplasty. Right ventricular improvement in 25 children after operation was analyzed. The correlation between postoperative oxygen saturation and postoperative right ventricular systolic blood pressure difference, the degree of pulmonary valve opening and the Z value of tricuspid valve ring in the non-stenting group were analyzed. Results: A total of 25 patients with PA-IVS were enrolled in the study, of whom 19 were males and 6 females, with an age at surgery of 12 (6, 28) days and a weight of (3.7±0.5) kg. One of them underwent only stenting of the arterial duct; 20 children underwent only percutaneous pulmonary valve perforation and balloon angioplasty; 4 children underwent both procedures. The Z-value of the tricuspid ring was -1.5±1.2 in the group with arterial duct stenting, and -0.1±0.4 in the group without stenting (t=2.77, P=0.010). The tricuspid regurgitant flow rate 1 month after surgery was significantly lower than the preoperative ((3.4±0.6) vs. (4.8±0.9) m/s, t=6.62,P<0.001). In the 24 children with percutaneous pulmonary valve perforation and balloon angioplasty, the preoperative right ventricular systolic blood pressure was (110±32) mmHg, and the postoperative systolic blood pressure was (52±19) mmHg (1 mmHg=0.133 kPa) (F=59.55, P<0.001). The factors that may affect postoperative oxygen saturation in 20 cases of non-stenting group were analyzed. The results suggested that the pre and post-operative right ventricular systolic blood pressure differences (r=-0.11, P=0.649), and the pulmonary valve orifice opening (r=-0.31, P=0.201) and tricuspid annulus Z value (r=-0.18, P=0.452) at 1 month after the operation were not significantly correlated with the postoperative oxygen saturation. Conclusions: Interventional therapy can be used as the first choice for one-stage operation of PA-IVS. Percutaneous pulmonary valve perforation and balloon angioplasty are more suitable for children with well-developed right ventricles, tricuspid annulus, and pulmonary arteries. While the smaller the tricuspid annulus, the more dependent it is on the ductus arteriosus and thus patients are more suitable for arterial duct stenting.

Analysis of flow torques during opening and closing of high-frequency rotary directional control valve

A 2D high-frequency rotary directional control valve with a spool having two degrees of freedom for axial linear motion and circumferential rotation is proposed in this paper. The axial linear motion decides the maximum orifice area, and the circumferential rotation lets the orifice area change continuously. One of the known elements impacting valve function is the flow force. This paper systematically analyzes the steady and transient flow torques subjected to the valve through theoretical analysis, AMESim-Fluent joint simulation and experimental tests. The results show that: under a single variable, the flow torques of the 2D high-frequency rotary directional control valve initially increase and then decrease like the sinusoid curve with the rotation of the spool and reach the maximum when the orifice opening is 1/2, and the flow torques are always in the direction of orifice closing and want to close the orifice. When the orifice area increases, the flow torques are the resistance, preventing the spool from opening; when the orifice area decreases, the flow torques are the power, pushing the spool to close. The steady flow torques are proportional to the pressure drop. The direction of the transient flow torque is independent of the relative position of the spool groove and sleeve window, which proportional to the square root of the pressure drop, orifice area and rotational speed. The flow torques are so important in the control of valve and can not be negligible.

A new compressible flow model for pneumatic directional control valves

In this study, a new compressible flow model for small orifice openings in pneumatic proportional directional control valves has been proposed. It is crucial to precisely control pneumatic valves over all control ranges; yet, conventional flow models fail around the closed position of the valve. The main deficit of the existing studies in the literature is to assume constant values for the parameters of the flow model over changing operating conditions. It has been demonstrated that these rough assumptions are insufficient in precisely predicting the mass flow rate, particularly for small orifice openings. An enhanced experimental setup has been introduced to improve the effectiveness of the proposed model. The cracking pressure ratio and parameters of the model have been identified with experimental method. In the proposed model, new empirical coefficients have been established after a thorough investigation of the impact of supply pressure on the flow behavior of the valve. Validation studies of the model in both the filling and exhausting states of the valve have been carried out at various supply pressures and orifice openings, yielding rather promising modeling performances. In validation tests, the real pressure and the pressure produced by new model have been compared, and good agreement has been achieved with 0.0039% absolute error. According to the findings, the proposed improved flow model can be selected in precision pneumatic control applications.

ХРОНИЧЕСКИЙ РЕЦИДИВИРУЮЩИЙ ПОСТКОИТАЛЬНЫЙ ЦИСТИТ: СОВРЕМЕННЫЙ ВЗГЛЯД НА ПРОБЛЕМУ

Lower urinary tract infections (UTIs) are one of the most common clinical bacterial infections in women, accounting for almost 25% of all infections. UTIs are more common in women than in men, in a ratio of 8:1. Approximately 50-60% of women report at least one episode of a UTI in their lifetime, and by the age of 24, one in three will have symptoms of a UTI requiring antibiotic treatment. The most common inflammatory disease of the bladder in women is cystitis. During their lifetime, 20-25% of women suffer from acute cystitis, every third of them has a relapse of the disease within a year, and in 10% it becomes a chronic relapsing form. A form of recurrent cystitis is postcoital cystitis – cystitis that develops within 1-2 days after intercourse in women with a high opening of the external urethral orifice and its hypermobility, as well as in the presence of urethrohymenal adhesions.

An experimental study on the damping characteristics and tuning of the liquid column vibration absorber

This paper deals with an experimental investigation of the damping characteristics of the liquid column dynamic vibration absorber. The laboratory test rig of a single degree of freedom system integrated with a liquid column dynamic vibration absorber was designed and manufactured to study the efficiency of this type of dynamic absorbers. The system response has been measured and recorded by using a (DXL-345) accelerometer and data acquisition system. The effects of mass ratio, length ratio, and the opening ratio of the central orifice on the vibration reduction of the main structure in free vibration mode were evaluated. The results showed that the tuned liquid column vibration absorber has a good ability to reduce or eliminate unwanted vibration by the suitable selection of the combination of its design parameters. The maximum damping of the main system was achieved at the mass, length and orifice opening ratios equal to 7.7 %, 87% and 74% respectively.

Optimizing growth, linear and 3rd order nonlinear optical traits of potassium aluminium sulfate (KAS) crystal by tuning pH for photonic device applications

Grown crystals, optical transparency and z-scan plots in open and close aperture conditions of KAS. • Novel pH dependent crystal growth of KAS was done. • PXRD confirmed improved crystallinity with decrease in pH. • Optical transmittance enhanced with decrease in pH. • 3rd order nonlinear optical properties were tuned by change in pH. This investigation is first to report the optimized crystal growth of potassium aluminium sulfate (KAS) at different pH. The well-defined single KAS crystals have been grown at pH 3, 5 and 7 engaging the slow evaporation process. Crystal structure and lattice parameters of grown KAS crystals have been determined using the powder X-ray diffraction technique. The impact of pH on optical transparency of KAS crystal is studied within 200–1000 nm through UV–visible optical analysis. He-Ne laser assisted Z-scan method is used to analyse third order nonlinear optical (TONLO) attributes of KAS crystal grown at alike pH. TONLO phase modification in refraction of grown crystals is inferred by Z-scan in close aperture configuration while the nonlinear absorption nature was sightseen by open orifice Z-scan. The Z-scan data has been used for comparative evaluation of TONLO refraction (n 2 ), susceptibility (χ 3 ) and absorption (β) coefficient of KAS crystals.

Hydrodynamic and acoustic pressure fluctuations in water pipes due to an orifice: Comparison of measurements with Large Eddy Simulations

The present article investigates the turbulent wall pressure fluctuations due to flow through single-hole sharp-square-edged orifices (opening area ratios of 11%, 20% and 31%) in a water-filled pipe by means of measurements and incompressible Large Eddy Simulations (LES) for opening area ratios of 20% and 31%. The orifice plate thickness was half the orifice diameter. The static pressure measurements and simulations show that the vena-contracta factors of the orifices are dependent on Reynolds numbers, which is due to the finite thickness of the orifices. These LES simulations provide a good prediction of the near-field hydrodynamic wall pressure fluctuations, which dominate up to the first three pipe diameters downstream of the orifice. Upstream and far downstream wall pressure fluctuations are dominated by acoustic pressure fluctuations. The source of the radiated sound field was estimated from the surface integral of the fluctuations across the orifice in the LES. The sound field was calculated by implementing the sound source in a one dimensional acoustic model of the test section. The power spectrum density (PSD) of the wall pressure fluctuations for pipe Reynolds numbers varying from 4000 to 10000 collapsed when presented in dimensionless form, which uses the dynamic pressure in the orifice as reference pressure and the ratio of cross-sectional averaged orifice velocity and orifice diameter as characteristic frequency. In the inertial range of the turbulence a global decay of the pressure PSD and of the sound source show a power of the Strouhal number between −113 and −2.8. For higher frequencies the pressure fluctuations were dominated by acoustic resonances. For wider orifices the magnitude of these acoustic pressure fluctuations is predicted within a factor two by the acoustic model. For the narrowest orifice (opening ratio of 11%) the measured PSD of pressure fluctuations displays sharp peaks due to self-sustained oscillations (whistling). A simple power law of the sound source is not accurate due to the unstable hydrodynamic modes related to orifice thickness. However, using the simple model for the sound source the acoustic model predicts the acoustic pressure fluctuations reasonably well for all orifices. At low frequency one observes a peak in the PSD hydrodynamic wall-pressure fluctuations at one pipe diameter downstream of the orifice. It is probably due to an acoustically silent “edge-tone-like” sinusoidal self-sustained motion of the jet.