Duct Length Research Articles

Optimization Study of Air Distribution of Flask Exhaust Hood Based on the Ceiling Attached Jet

Pouring is an important process in foundry. However, due to the large number of risers and unfixed flask position, the high-temperature smoke generated by the flask is difficult to collect, which has a negative impact on the working environment and atmospheric environment of the workshop. Solving the environmental problems caused by flask is a focus of green development of foundry industry. In this paper, the effect of flask smoke exhaust hood based on the ceiling attached jet is studied. The air distribution in the exhaust hood is optimized by numerical simulation to avoid the escape of contaminants from the hood. The main influencing factors such as length of air supply duct, flask temperature and air distribution optimization device in the hood were studied. The results show that the ceiling attached jet method can improve the capture efficiency of the exhaust hood. The best capture efficiency is achieved when the length of the air supply duct is 3m. The air distribution can be significantly improved when the length of the baffle is greater than 600mm. Compared with the existing technical scheme, this study can save energy25×104kWh/a, the total particulate emissions are reduced by 97%. This study has important reference significance for the green development of foundry industry.

Discussion of the Fluid Acceleration Quality of a Ducted Propulsion System on the Propulsive Performance

This paper focuses on the ducted propulsion with the accelerating nozzle, and discusses the influence of its fluid acceleration quality on its propulsive performances, including the hull efficiency, the relative rotative efficiency, the effective wake, and the thrust deduction factor. An actual ducted propulsion system is used as an example for computational analysis. The computational conditions are divided into four combinations, which are provided with different propeller pitches, cambers, and duct lengths. The method applied in this study is the Computational Fluid Dynamics (CFD) technology, and the contents of the calculation include the hull's viscous resistance, the wave-making resistance, the propeller performance curve, and the self-propulsion simulation in order to obtain the ship's effective wake, thrust deduction factor, hull efficiency, and relative rotative efficiency. The performance curve of the propeller and resistance estimation results are compared with the experimental values for determining the correctness of the self-propulsion simulation. According to the computational analysis, it is known that increasing the propeller pitch cannot effectively increase the hull efficiency. The duct acceleration quality can be reduced by shortening the duct length; hence, when the effective wake fraction and thrust deduction factor decrease, the hull efficiency is increased. In addition, the pressure inside the duct is relatively low if the acceleration quality of the duct is too high, which is unfavorable for controlling the propeller cavitation. Moreover, if the hull bottom in front of the propeller is tapered up from the front to the back at an overly steep angle, the thrust deduction factor will be too large and lead to a relatively low hull efficiency.

Gas explosion venting of 20-litre vessel with and without various length of vent ducts

When gas explosion occurs in closed vessel, venting devices can reduce the pressure inside the protected equipment, and vent ducts can be used to direct burnt and unburnt mixtures. In this paper, some ductless and duct vented explosion measurements were performed in a standard 20-liter explosion chamber with 2.8 to 6.3 vol.% propane-air mixture at atmospheric pressure (1 barg) and ambient temperature (298 K). Experimental investigations were performed with different lengths of vent duct (0 meter, 0.15 meter, 1 meter). During the measurements, effects of vent ducts to the venting process had been studied. Aluminium foils were used as rupture disks with 30 mm diameter circular venting area. During each measurement, static activation overpressure of aluminium foil, maximum explosion overpressure of propane-air mixture, the gas deflagration index in case of the vented vessel, and the pressure drop along the 1 meter length duct were determined.

Effect of duct type, size, and embedment on bond behavior of post-tensioned mono-strand concrete members

This research investigated the bond behaviour of mono-strand post tension systems with different duct types, sizes, and embedment length. Six specimens were considered in this study. Two different types of ducts were considered: plastic ducts and galvanic ducts. Two different duct sizes (9 cm × 4.2 cm and 6 cm × 2.4 cm), and embedment lengths (5 cm and 10 cm) for each duct type were considered in this study. Results showed that specimens with galvanic ducts had stronger bond than those with plastic ducts. In addition, it was found that extending the embedment length of the galvanic ducts form 5 cm to 10 cm improved the bond strength which was not the case for plastic ducts where the effect was null. Furthermore, specimens with galvanic ducts had greater bond strength when duct size was increased than those with plastic ducts.

Dejstvo i značaj varijacija anatomije ekstrahepatičnih žučnih kanala u etiologiji holedoholitiaze

Background: Biliary stone disease is a frequently encountered problem among the population with a variety of causes and resulting in a wide range of symptoms from vague abdominal discomfort to life-threatening conditions requiring urgent surgical intervention. Magnetic resonance cholangiopancreatography (MRCP) has become a noninvasive radiological diagnostic method extensively used in the evaluation of the biliary tract providing excellent anatomical detail. Apart from the classical causes widely described in the literature in stone etiology, the effect of anatomical variations of the bile tract is a subject that has been investigated recently. The present study aimed to manifest the effect of anatomical variations of the extrahepatic biliary tract on the etiology of choledocholithiasis. Methods: The data of 182 patients who underwent MRCP in our hospital between 2016 and 2021 were retrospectively scanned. The patients were divided into two groups, asymptomatic patients and acute cholangitis. Cystic duct, common hepatic duct, choledochal lengths, and variations in cystic duct opening were analyzed by an experienced radiologist in MRCP. Results: The relation was detected between the cystic choledochal variance of the patients (p<0.001). The cystic duct length of the patients showed statistically significant differences (p<0.05). Conclusion: When the extrahepatic bile duct variations were evaluated, some notable values were found for the etiology, as well as being critical in acute cholangitis. There is a need for studies with larger sample sizes in the literature on this subject.

Anatomy-Based Frequency Allocation in Cochlear Implantation: The Importance of Cochlear Coverage.

This study aimed to compare the predicted anatomy-based frequency allocation of cochlear implant electrodes with the default standard frequencies. Retrospective study. A retrospective analysis was performed using computed tomography (CT) images of patients who received cochlear implants at a tertiary referral center. Patients were excluded if they had any congenital or acquired cochlear anatomical anomalies. The CT images of the patients were uploaded to the surgical planning software. Two independent reviewers allocated the anatomical parameters of the cochlea. The software then used these parameters to calculate the frequency allocation for each electrode according to the type of electrode and the length of the organ of Corti (OC) in each patient. These anatomy-based frequency allocations were compared with the default frequency settings. Frequency-to-place mismatch in semitones. A total of 169 implanted ears in 102 patients were included in this study. The readings of the two reviewers were homogenous, with a Cronbach's alpha of 0.98. The mean anatomy-based frequency allocation was 487.3 ± 202.9Hz in electrode 1; 9,298.6 ± 490.6Hz in electrode 12. The anatomy-based frequency allocations were found to be significantly higher than the frequencies of the default frequencies for each corresponding electrode (one-sample t-test, P < .001). The frequency-to-place mismatch was negatively correlated with cochlear coverage and positively correlated with the cochlear duct length (Pearson correlation > 0.65, P < .003). The anatomy-based frequency allocation of each electrode is significantly different from the default frequency setting. This frequency-to-place mismatch was affected mainly by the cochlear coverage. 3 Laryngoscope, 132:2224-2231, 2022.

Influence of abrupt increase in relief and the flow pattern in CD nozzle

In this investigation, experiments are done for Mach 1.25, 1.3, 1.48, 1.6, and 1.8 for different duct lengths and the nozzle pressure ratio to evaluate the microjets' control effectiveness for a duct diameter ratio of 2.5 to assess the influence microjets as dynamic control on the flow field in the duct and efficiency of the control. These Mach numbers are selected as the base drag will maximum at transonic low low supersonic Mach numbers. The NPRs selected are such that the flow will be over, under, and perfectly expanded and how dynamic control responses under these level of expansion. The results indicate that the flow pattern in the pipe is matching for most of the instances. However, the results are shown only for combining parameters with a discrepancy in the stream pattern due to a stream management mechanism. The results show no definite trend, and control results in both positive and negative trends inside the duct flow field. The control efficacy is a resilient function of NPR. For lower NPRs, the minimum duct requirement is 3D, but at higher NPR and lower Mach, the stream continued connected with the duct for 2D length. The marginal change in the inertia level does the flow pattern in the pipe.

Variations of Cystic Duct and Its Clinical Significance

Background: Cystic duct drains the bile from the gallbladder into the common bile duct. Gallstone disease is one of the most common problems affecting the digestive tract and may lead to many complications. To avoid the complications in these patients the gallbladder is removed surgically (Cholecystectomy). Ligation of cystic duct and cystic artery is a prerequisite procedure when cholecystectomy is done. Understanding about the normal anatomy &amp; the possible variations in biliary ductal system is important for the surgeons for doing cholecystectomy surgery successfully. Errors during gallbladder surgery commonly result from failure to appreciate the common variations in the anatomy of the biliary system. Aim of the study: To find out the incidence of variations in the length, course, and termination of cystic duct in cadavers. Materials and Methods: Present study was done in 50 adult cadavers in the Department of Anatomy, Government Tiruvannamalai medical college, Tamilnadu. Meticulous dissection was done in the hepatobiliary system of these cadavers. Observations: During the study variations in the length of cystic duct, course and different modes of insertion of cystic duct were observed. Conclusion: Knowledge of variations in the length of cystic duct and knowing about different modes of course &amp; insertion of cystic duct is necessary for surgeons while conducting cholecystectomy. The risk of iatrogenic injury is especially high in cases where the biliary anatomy is misidentified prior to surgery. KEY WORDS: Cystic duct, Gallbladder, Cholecystectomy.

External Negative Pressure Drainage of the Pancreatic Duct in Pancreatogastrostomy Following Pylorus-Preserving Pancreaticoduodenectomy-Feasibility and Technique.

Background: Postoperative pancreatic fistula (POPF) is a major cause of morbidity after pancreaticoduodenectomy. There is no consensus on the best technique to protect the pancreato-enteric anastomosis and reduce the rate of POPF. This study investigated the feasibility and efficiency of external suction drainage of the pancreatic duct to improve the healing of pancreaticogastrostomy.Methods: Between July 2019 and June 2021, 21 consecutive patients undergoing elective pancreaticoduodenectomy were included. In all patients we performed a pancreaticogastrostomy and inserted a negative pressure drainage into the pancreatic duct. The length and diameter of the pancreatic duct were measured and the texture of the pancreas was evaluated. The daily secretion volume and the lipase value via pancreatic duct drainage were documented. The occurrence of POPF was evaluated.Results: None of the patients had drainage-related complications. In 4 patients we registered a dislocation of the drainage from the pancreas duct into the stomach. 17/21 Patients showed no signs of POPF. A biochemical leak was measured in one patient. Furthermore, 2 patients had a POPF grade B. In one patient, POPF grade C required reoperation and resection of the remnant pancreas. All 4 cases of POPF met the risk criteria soft pancreas, high volume and high lipase value in the duct drainage.Conclusion: The insertion of the pancreatic duct drainage was feasible and caused no drainage-related morbidity. POPF-rate was moderate in the risk population of soft pancreas and small duct.

Active control behavior on the flow pattern in a circular duct

The current analysis aims to review the effectiveness of the flow regulations at Mach 1.87, a considerably large Mach number. The duct radius is11 mm, and the diameter ratio concerning the exit of the nozzle is 2.2. Tests were done at different expansion levels for eight different duct sizes. Here we are pondering in a situation where there is a considerable variation of pressure is noticed. The flow control was located at a PCD of 13 mm from the axis. The control jets of 0.001 m diameter producing a Mach unity jet, used as energetic flow control. For shorter tube sections at smaller NPRs, the pressure undertakes a minimal value. Soon After, with an increase of the tube size and expansion levels, a continuing fall in pressure owing to the decline in the level of adverse pressure and shock waves intensity. Flow fluctuations are witnessed for various duct sizes. The duct size represents a vital part while ascertaining the flow advancement in the duct. Relatively high pressure is seen for duct length L = 132 mm and L = 220 mm for nozzle pressure ratios three and five. The pressure becomes modest due to the effect of duct size. For NPR = 7, an increase in pressure is restricted by the separated zone, and atmospheric restrictions are almost accomplished. For the 10D duct, the realization of the ambient condition is additionally enhanced near the upstream.

Waveguide for air-coupled ultrasonic phased-arrays with propagation time compensation and plug-in assembly.

Waveguides allow grating lobe free beamforming for air-coupled ultrasonic phased-arrays by reducing the effective inter-element spacing to half wavelength. Since the sound waves propagate through the waveguide ducts, additional time delays are introduced. In this work, we present analytical, numerical, and experimental methods to estimate these time delays. Afterwards, two different waveguides are compared. The first one consists of equal-length ducts, requiring a time-consuming assembly process of the ultrasonic phased-array. In contrast, the second waveguide consists of Bézier-shaped ducts of unequal lengths but a planar input port allowing fast assembly. The analytical model is based on the geometric lengths of the waveguide ducts. The numerical model relies on a transient finite element analysis. All simulations are validated in an anechoic chamber using a calibrated microphone. The analytical (7.6% deviation) and numerical (3.2% deviation) propagation time models are in good agreement with the measurements. By using the analyzed propagation times for the compensation of the unequal waveguide duct lengths, we restored the beamforming capability without significant sound pressure level (SPL) loss. This work shows the possibility of reduced transducer assembly time for waveguided air-coupled phased-arrays without a reduced SPL.

Anatomy of the parotid duct: Assessing variations of the parotid gland drainage pattern

IntroductionThe parotid duct drains the parotid gland, the largest of the human salivary glands. The PD receives an accessory PD from the accessory PG, a variation of the PG often mistaken for a soft tissue mass. The PD's superficial location contributes to the occurrence of iatrogenic and traumatic duct injuries. Case reports suggest that variations in the form of duplicated PDs, have resulted in clinical complications. Therefore, an observational, cross-sectional study was designed to determine the anatomical variations in the PG drainage pattern via the PD. Materials and methodsThe left and right parotid regions of 20 embalmed cadavers (N = 40) at Stellenbosch University were dissected. Latex was injected into the oral papilla for better visualisation of the duct. The duct lengths were measured and classified. The anatomical variations of the PD were documented. ResultsSix of the 40 parotid regions were excluded due to damage. Bilateral PD duplication was observed in one cadaver (5.88%), while the remaining 94.12% presented with single PDs. The mean duct length on the left and right sides were found to be 48.5 mm and 45.9 mm respectively. Additionally, accessory PGs were identified in 50% of cadavers. ConclusionsWhile rare, bilateral double PDs were identified in this sample. This highlights the importance of understanding anatomical variations of the PG drainage pattern via the PDs, including the incidence of accessory PGs, to limit the occurrence of unnecessary iatrogenic injury, such as compression of the duct causing salivary retention in the PD following a Rhytidectomy, and effectively repair traumatic duct injuries. Further research should be conducted to investigate the branching pattern of the PD within the PG.

Comparative investigation of the aerodynamic performance for several Shrouded Archimedes Spiral Wind Turbines

Wind energy is one of the most rapidly developing renewable energy technologies. Conventional turbines, which are commercially available in some cities, are designed to run at relatively high speeds to be sufficiently effective but not in the urban areas. A new type of horizontal axis wind turbine, namely, Archimedes Spiral Wind Turbine (ASWT) is designed for urban usage. The aerodynamic performance of the ASWT was examined using numerical analysis. To improve the possibility of wind power use within the range of low speeds, a wind lens has been used to enhance the efficiency of the ASWT to enhance the flow characteristics through the rotor blades. The current analysis focuses on design the best configuration of wind-lens that shrouding the ASWT. The current work investigates the wind-lens' design parameters, such as the diffuser length, diffuser angle, duct length, and flange height. Thus, to obtain the maximum performance output of the Shrouded Archimedes Spiral Wind Turbine (SASWT). The CFD results showed that shrouding the turbine increases the peak power coefficient and the mass flow rate through the rotor plane. The maximum power coefficient, CP obtained from the analysis for the best configuration of SASWT was 0.49 at TSR = 3. The maximum CP for SASWT increased by 2.1 times compared with the ASWT.

Cochlear Pathomorphogenesis of Incomplete Partition Type II in Slc26a4-Null Mice.

Incomplete partition type II (IP-II) is frequently identified in ears with SLC26A4 mutations. Cochleae with IP-II are generally observed to have 1½ turns; the basal turns are normally formed, and the apical turn is dilated or cystic. The objective of this study was to characterize the pathomorphogenesis of the IP-II cochlear anomaly in Slc26a4-null mice. Otic capsules were dissected from Slc26a4Δ/+ and Slc26a4Δ/Δ mice at 1 and 8days of age and at 1 and 3months of age. X-ray micro-computed tomography was used to image samples. We used a multiplanar view and three-dimensional reconstructed models to calculate the cochlear duct length, cochlear turn rotation angle, and modiolus tilt angle. The number of inner hair cells was counted, and the length of the cochlear duct was measured in a whole-mount preparation of the membranous labyrinth. X-ray micro-computed tomography mid-modiolar planar views demonstrated cystic apical turns in Slc26a4Δ/Δ mice resulting from the loss or deossification of the interscalar septum, which morphologically resembles IP-II in humans. Planes vertical to the modiolus showed a similar mean rotation angle between Slc26a4Δ/+ and Slc26a4Δ/Δ mice. In contrast, the mean cochlear duct length and mean number of inner hair cells in Slc26a4Δ/Δ mice were significantly smaller than in Slc26a4Δ/+ mice. In addition, there were significant differences in the mean tilt angle and mean width of the modiolus. Our analysis of Slc26a4-null mice suggests that IP-II in humans reflects loss or deossification of the interscalar septum but not a decreased number of cochlear turns.

Inertia and expansion level impact on flow development at various duct sections

This study aims to investigate the effect of expansion on the flow of the duct. The pipe diameter is 18 mm, and tests were done at Mach 1.8, 2.0, and 3.0. When there is an adverse pressure gradient at the nozzle exit, the wall pressure attains high values due to the oblique shock. For this case, once the flow control technique is used, the pressure reduces in the duct. At the design nozzle pressure ratio (NPR), the wall pressure results show a similar pattern for Mach 1.8 and 2.0. Among them, marginal variations are seen due to the change in the duct length, impact of the backpressure, and interaction of the shock waves. However, at tube section 2D, the stream continued fastened to the wall tube. The stream pattern with and without control are similar. There is a minimal variation in the duct's stream pattern, and the normalized wall pressure fluctuations are large. Despite the stream being fastened to the tube's wall for the lowest duct length, the pipe pressure attains the ambient pressure value due to the freestream pressure impact.

Under-expansion jet flame propagation characteristics of premixed H2/air in explosion venting

In premixed H2/air explosion venting, an under-expansion jet may be caused by the pressure difference between the inside and outside of the explosion vent. Based upon the under-expansion jet, studying the structure of the under-expansion jet flame and the factors influencing its formation is essential to hydrogen safety in explosion venting. This study explored the basic characteristics of the under-expansion jet flame in premixed H2/air explosion venting, and discussed the formation of two under-expansion structures (Mach disk and diamond shock wave) of such jet flames by conducting a premixed H2/air explosion venting experiment. The influences of hydrogen fraction, explosion venting diameter, and duct length on the structure of under-expansion jet flames were evaluated. The results showed that after successful explosion venting, the under-expansion jet flame would be generated when the hydrogen fractions were 30–60 vol.%, and as the hydrogen fractions were 30–50 vol.%, the lengths of the venting duct were 30 and 50 cm. The duration of under-expansion jet flame was the longest when the hydrogen fraction was 40 vol.%. With the explosion venting diameter and hydrogen fraction increased, the spacing between under-expansion jet flame structures (S) increased. However, an increase in duct length led to the attenuation of the S. During the explosion venting, the under-expansion jet caused a pressure imbalance near the explosion vent and high-intensity convection forms on both sides of a jet, which can generate two or more explosions. Therefore, understanding the basic characteristics of under-expansion jet flame can aid the effective development of measures to prevent, mitigate, and protect against premixed H2/air explosions.

S1689 Anomalous Biliary-pancreatic Junction: A Case of Recurrent Pancreatitis and Implicit Bias

Introduction: Implicit bias is defined as the attitudes or stereotypes that unconsciously affect our understanding, actions, and decisions. Physicians must make a concerted attempt not to fall prey to implicit bias as this can lead to differences in the quality of care between patients. We describe a case of implicit bias secondary to a diagnosis of anomalous biliary pancreatic junction (ABPJ). Case Description/Methods: A 50-year-old Hispanic woman with an extensive psychiatric history, polysubstance abuse, and recurrent pancreatitis presented with abdominal pain. Given her history, the etiology of recurrent pancreatitis was deemed to be due to polysubstance abuse. CT abdomen showed a dilated common bile duct, dilated pancreatic duct, and pancreatic calcifications consistent with a history of chronic pancreatitis. Review of previous medical records showed that a prior MRCP had revealed duplication of the biliary ductal system. The medial duct draining the right lobe of the liver, anastomosed with the pancreatic duct to form a common channel that opened into the duodenum. The lateral duct drained the left lobe of the liver and opened it into the duodenum through a separate papilla. Gastroenterology was consulted and a diagnosis of ABPJ was made. Consequently, the patient's episodes of pancreatitis were thought to be secondary to ABPJ. Patient then underwent an ERCP with pancreatic sphincterotomy and stent placement, leading to significant symptom resolution. Discussion: ABPJ is a congenital malformation where the biliary and the pancreatic ducts join outside the wall of the duodenum. Incidence is estimated to be 1.5 – 3.2 % among all patients that undergo an ERCP. Since the function of the duodenal papilla does not traverse the length of the common duct, regurgitation of pancreatic and biliary secretions occurs. In most cases, the pressure in the pancreatic duct is higher, resulting in the reflux of pancreatic juice into the biliary tract and subsequent development of biliary tract malignancy. In a rare minority of cases, bile can reflux into the pancreatic ductal system, causing recurrent pancreatitis. ABPJ is a rare and under-recognized cause of recurrent pancreatitis in the adult population. Often, the diagnosis of ABPJ is overshadowed by the treating physician’s implicit bias due to patient factors such as ethnicity, age, past medical history, etc. A high index of suspicion is required to make an accurate diagnosis leading to prompt intervention, thus avoiding delay in care and associated morbidity.Figure 1.: CT scan showing collection in Gall Bladder fossa.

Influence of electrode to cochlear duct length ratio on post-operative speech understanding outcomes

Objective To assess whether the pre-operative electrode to cochlear duct length ratio (ECDLR), is associated with post-operative speech recognition outcomes. Study Design A retrospective chart review study. Setting: Tertiary referral center. Patients The study included sixty-one adult CI recipients with a pre-operative computed tomography scan and a speech recognition test 12 months after implantation. Interventions The average of two raters’ cochlear duct length (CDL) measurements and the length of the recipient’s cochlear implant electrode array formed the basis for the electrode-to-cochlear duct length ratio (ECLDR). Speech recognition tests were compared as a function of ECDLR and electrode array length itself. Main outcome measures The relationship between ECDLR and percent correct on speech recognition tests. Results A second order polynomial regression relating ECDLR to percent correct on the CNC words speech recognition test was statistically significant, as was a fourth order polynomial regression for the AzBio Quiet test. In contrast, there was no statistically significant relationship between speech recognition scores and electrode array length. Conclusions ECDLR values can be statistically associated to speech-recognition outcomes. However, these ECDLR values cannot be predicted by the electrode length alone, and must include a measure of CDL.

Measuring 3D Cochlear Duct Length on MRI: Is It Accurate and Reliable?

Prior studies have evaluated cochlear length using CT to select the most suitable cochlear implants and obtain patient-specific anatomy. This study aimed to test the accuracy and reliability of cochlear lateral wall length measurements using 3D MR imaging. Two observers measured the cochlear lateral wall length of 35 patients (21 men) with postlingual hearing loss using CT and MR imaging. The intraclass correlation coefficient (with 95% confidence intervals) was used to evaluate intraobserver and interobserver reliability for the 3D cochlear measurements. The mean age of the participants was 39.85 (SD, 16.60) years. Observer 1 measured the mean lateral wall length as 41.52 (SD, 2.25) mm on CT and 41.44 (SD, 2.18) mm on MR imaging, with a mean difference of 0.08 mm (95% CI, -0.11 to 0.27 mm), while observer 2 measured the mean lateral wall length as 41.74 (SD, 2.69) mm on CT and 42.34 (SD, 2.53) mm on MR imaging, with a mean difference of -0.59 mm (95% CI, -1.00 to -0.20 mm). An intraclass correlation coefficient value of 0.90 (95% CI, 0.84-0.94) for CT and 0.69 (95% CI, 0.46-0.82) for MR imaging was obtained for the interobserver reliability for the full-turn cochlear lateral wall length. CT-based 3D cochlear measurements show excellent intraobserver and interobserver reliability, while MR imaging-based lateral wall length measurements have good-to-excellent intraobserver reliability and moderate interobserver reliability. These results corroborate the use of CT for 3D cochlear measurements as a reference method and demonstrate MR imaging to be an alternative acquisition technique with comparably reliable results.

Impact of microjets on the flow of a duct

This study investigates the streaming development in the tube and pressure recovery once the flow regulator is activated in the recirculation zone at a different level of expansions. The Mach numbers considered are 1.87, 2.2, 2.58. The duct diameter is 16 mm. Tiny jets of 1 mm diameter are placed at the midplane of the base to regulate the flow. The control jet’s Mach number is unity as they are circular orifice despite the NPR of the control jet being very high. The investigations reveal that the stream remained connected with the duct even for L = 1D for the entire Mach numbers. The pressure’s initial values are very high for an over-expanded nozzle than the under-expanded and ideally expanded nozzles. From the wall duct field, it is seen that the flow becomes oscillatory for lengths L = 10D to 6D owing to the collaborations of the waves, the duct wall, and the influence of the ambient pressure. The recovery of the tube pressure also gets shifted towards the downstream for the more considerable duct lengths. The flow quality with and with no flow control mechanism is identical for duct lengths 10D and 8D. Lower duct lengths show mixed trends regarding flow development, and the flow’s quality is concerned. The flow control mechanism is effective once the nozzle flows with favorable pressure or at the design NPRs. When the nozzle has more pressure than ambient values, the control becomes useful, quickly raising the pressure’s values.