Exit Area Research Articles

A computational investigation of shock wave train in diverse duct geometries using machine learning-adopted k-ω turbulence model

This research paper presents a thorough examination of shock wave train phenomena in various duct structures, utilizing a machine learning-optimized k-ω model. The focus of the study is to apply machine learning techniques to adapt the constant coefficients of the k-ω turbulence model, improving its accuracy and computational efficiency in capturing the dynamics of shock waves. An important aspect of this investigation is the impact of diverging sections within the duct, specifically how changes in the divergence angle, while maintaining a constant ratio of the exit area to the throat area, affect compressible flow parameters, shock wave positions, and other related characteristics of shock trains. The study systematically explores these effects and provides fresh insights into the behavior of shock wave trains under different divergence conditions. In a departure from the usual practices in supersonic research, this study compares the phenomena of shock wave trains in rectangular and circular duct geometries. The findings contribute valuable data and analyses to a field that has traditionally focused on rectangular configurations. The results indicate that the shape of the duct has a significant influence on the shock wave train, emphasizing the importance of considering geometric diversity in the study of supersonic flows and shock wave phenomena. This research sets the stage for further investigations into the interaction between duct geometry, shock wave propagation, and the dynamics of compressible flows.

Tool Dynamics-induced Surface Topography Error in Fast Tool Servo-Based Diamond Turning of Micro Dome Arrays

Micro dome arrays are applied as moulds to injection/press moulding to produce micro lens arrays. Fast tool servo (FTS) based diamond turning is a promising technique for manufacturing such micro dome arrays with high accuracy and machining efficiency. In this study, cutting of micro dome array (MDA) on copper with FTS was performed to evaluate the dynamics behaviour of the tool servo and its effects on surface topography. Results show that local surface speed dramatically affects the servo dynamics behaviour. When the local surface speed is higher than a critical value, overcutting and wavy patterns could be formed on the cut-in area of the domes and exit area, which is caused by the servo response and its limitation. By capturing and analysing the position signal and correlating it with the surface topography of the generated dome surface and considering its limitations, an effective strategy for optimizing micro dome array machining parameters was proposed. MDA cutting tests with optimized cutting conditions achieved a significantly improved form accuracy. This study will guide the optimal use of FTS systems in machining micro structured surfaces.

Evaluation of Cytogenetic Damage Induced during Hysterosalpingography Procedure: A Cross-sectional Study

Introduction: Hysterosalpingography (HSG) is a radiographic procedure used to visualise the fallopian tubes and uterine cavity by injecting a contrast medium, commonly employed for diagnosing infertility cases. However, due to the associated radiographic and fluoroscopic exposure, there is an increased risk of chromosomal damage to the gonads. Aim: To investigate the impact of radiographic and fluoroscopic exposure on chromosomal integrity in peripheral blood lymphocytes using the Cytokinesis Blocked Micronucleus (CBMN) assay. Materials and Methods: This cross-sectional time-bound study included 10 patients (n=10) scheduled for HSG procedures at the Department of Radiology, Justice KS Hegde Hospital, Mangaluru, Karnataka, India from April 2021 to March 2022. Following radiation exposure, the CBMN assay was conducted to evaluate chromosomal damage in both test and control group blood samples. Blood samples from healthy donors were divided into three cryo vials, with one serving as the control and the remaining two exposed to radiation at the entrance and exit areas during the HSG procedure. The data were expressed as mean±Standard Deviation (SD). A p-value <0.05 was considered statistically significant. The analysis was performed using Statistical Package for Social Sciences (SPSS) version 20.0. Results: A statistically significant (p<0.05) increase in biological damage was observed when comparing the Micronucleus (MN) frequency of the test groups (entrance=0.022±0.005 and exit group=0.0172±0.005) with the control group (0.006±0.003). Additionally, a decrease in MN frequency was noticed within the test groups, particularly in the exit group, although the results were not statistically significant (p=0.066). Conclusion: The HSG is an effective clinical diagnostic technique. However, the present study indicates a potential risk of chromosomal damage associated with the procedure, emphasising the need for judicious use of radiation exposure during HSG.

Juridical Analysis of the Authority of Quarantine Officials in Handling Illegal Cattle Importation on Batam Island

The government has established regulations related to the entry of cattle or the movement of animal carrier media between domestic entry or domestic exit areas, namely Law Number 21 of 2019 concerning Quarantine of Animals, Fish and Plants. This regulation is intended to prevent the entry and spread of HPHK, HPIK, and OPTK from one area to another within the territory of the Unitary State of the Republic of Indonesia, but the reality in the field is that there are still violations of cattle entry into Batam Island not in accordance with applicable laws and regulations. This study aims to determine how the implementation of the authority of quarantine officials in handling illegal cattle importation in Batam Island. This research uses qualitative research. Normative legal research method supported by sociological legal research, this research requires primary, secondary and tertiary legal materials. The obstacles faced in the implementation of quarantine are caused by less than optimal supervision, lack of public understanding of the Quarantine Law, economic factors where to fulfill the quarantine requirement documents require costs which according to them are not small, regulations and the time required in processing other required documents there is no certainty of time. The solution in dealing with these obstacles is to strengthen quarantine carried out on all sides in synergy with other related agencies, community participation who actively comply with the law and care about the importance of efforts to prevent the entry and spread of HPHK. Regular training and knowledge updates to ensure that quarantine officials are always ready to deal with various possible threats that arise. The results of the study show the implementation of the authority of quarantine officials in carrying out quarantine measures against carrier media, especially animals based on applicable laws and regulations by taking into account disease status and risk analysis in order to keep livestock healthy and food safety, ensuring the health of meat to be consumed by the public. In certain conditions there are still violations that occur with various factors. The community and government agencies and law enforcement can coordinate and supervise the movement of carrier media, especially animal traffic so as to maintain the transmission and spread of disease in animals that have an impact on health and food safety for the community.

CHARACTERIZATION OF FULLY DEVELOPED AIR-ASSISTED SPRAY UNSTEADINESS USING RP-3 JET FUEL

The ideal spray theory of Edwards and Marx was utilized to investigate the dependence of fully developed intermittent air-assisted spray unsteadiness on operational conditions and fluid properties. Time series information of spray droplets was identified by phase Doppler particle analyzer and used for inter-particle arrival time statistics. Results demonstrated that spray unsteadiness along the spray axis and in proximity to the nozzle exit area is more pronounced than far-nozzle field and spray periphery. The unsteadiness on the spray axis exhibits a decreasing function with the fuel injection durations, whereas an increase of air injection duration significantly elongates the unstable region along the spray axis. The properties of test liquid fuels show a moderate effect on the unsteadiness of the air-assisted spray, potentially due to their inconspicuous influences on spray atomization characteristics. Chi-square method is generally the preferred method for quantifying the global spray unsteadiness when compared to the deviation of the first time gap of experimental and theoretical inter-particle time distribution. Unsteadiness results observed during high-velocity droplet spray stage are relatively distinct compared to droplet deceleration and suspension stages. This distinction can be attributed to the continuous energy input during the initial nozzle opening, emphasizing the significance of droplet velocity in determining spray unsteadiness.

Analysis of Scattered Radiation Dose in Cardiac Catheterization Examination in the Cathlab Room Using TLD

The problem: About 75% of the information humans receive visually or through the eyes. However, the eye cannot detect all types of light, including X-ray radiation. There are parts of the human body organs are very sensitive to X-ray radiation, because of the risk of damaging tissues and triggering causing ery, infertility or cataracts. Today, X-rays have become the backbone of the development of radiology equipment, especially for producing. One of them is C-Arm equipment technology, which is able to image three-dimensional patient objects in real time with fluoroscopy techniques. This study aims to obtain and evaluate the effective radiation dose received by medical personnel working in the cathlab room area when radiation workers during cardiac catheterization is performed. Observations were made in 10 radiation measurement areas, namely the radiographer operator area, the area in and out of medical personnel, the area in and out of patients, the Pb glass area in the operator room, the Pb glass area in the Cathlab examination room, the area where TLD measurements are placed waist-high doctors, nurses and radiographers work during the installation of the heart ring, the floor area near the X-ray source, and the wall area in the Cathlab examination room. The main tool uses C-Arm modality, and TLD detector chips. The object of observation is the radiation source area consisting of one doctor, one radiographer and one nurse. Catheterization was performed on 10 patients with different examination times. Research results: operator area; the effective dose received was 0.000 mSv, doctors ranged from 1.136 to 3.608 mSv, while nurses ranged from 0.194 mSv to 2.270 mSv, while radiographers ranged from 0.074 mSv to 0.126 mSv, while patient entrance and exit areas ranged from 0.00 mSv to 0.0127 mSv, while nurses in and out of medical personnel ranged from 0.005 mSv to 0.057 mSv, Measurements on the floor near the radiation source/floroscopy range from 0.036 mSv to 0.074 mSv. Cathlab indoor wall measurement results range from 0.031 mSv to 0.103 mSv. Within 1 year, the dose in the operator room is 0.00 mSv, the dose received by doctors ranges from 230.4 to 1209.5 mSv/hour, radiographers between 128.2 mSv to 1812.4 mSv and nurses between 115.2 mSv to 2448.2 mSv. In the area of the patient entrance and exit between 0.00 mSv to 38.8 mSv, the area of the patient entrance and exit between 72.00 mSv to 82.2 mSv, and the floor area near the radiation source/floroscopy between 518.2 mSv to 1065.2 mSv, as well as the inner wall area of the cathlab chamber between 44.6 mSv to 148.32 mSv. It was found that; The effective dose received in one year received by doctors, nurses and radiographers who work close to radiation sources (floroscopy) results are higher than the dose value set by PERKA BAPETEN No. 8 of 2011 which is 20 mSv and ICRP 203 which is 500 mSv per year.

Exploring the Impacts of Exit Structures on Evacuation Efficiency

In the context of a fire emergency, safe and efficient exits are of paramount importance for pedestrian evacuation. The recent rapid development in the construction industry has rendered exit structures more diverse and complex. However, little attention has been paid to the influence of exit structures on the efficiency of crowd evacuation processes. In this paper, a tentative experiment was designed to preliminarily reveal the effects of five exit structures (Exit 1, Exit 2, Exit 4, Exit 5, and Exit 3 as examples for comparison) on crowd evacuation. Exit 1 has door leaves opening outward. Exit 2 has door leaves opening inward. Exit 3 has no leaves. Exit 4 consists of double-layer exit doors with the doors opening outward. Exit 5 comprises double-layer exit doors with the doors opening both sides outwards Subsequently, according to the properties of this experiment, a social force-based simulation model was established using the AnyLogic software 8.8.4. By changing the exit width and the crowd density, data such as evacuation time, flow rate, crowd density, and time delay were investigated in detail. The results revealed a notable variation in the evacuation efficiency depending on the deign of the exit. The respective flow rates for Exits 1, 2, 3, 4, and 5 were 0.66 people/(m·s), 0.77 people/(m·s), 0.80 people/(m·s), 0.71 people/(m·s), and 0.66 people/(m·s). Although Exit 3 excelled in terms of evacuation efficiency, it is not directly applicable to real architectural structures. Therefore, Exit 2 emerged as a highly promising solution in terms of flow rate and population control in the exit area, underscoring the effectiveness and practicality of its structural design. It is prospective that the results of this study can offer engineering and technical professionals valuable references and guidance concerning the design of exit structures.

Numerical investigation on flow characteristics of multi-stream supersonic nozzle with serpentine configuration

The serpentine configuration is utilized in the multi-stream supersonic nozzle of the Adaptive Cycle Engine to improve the stealth performance of next-generation fighters. Compared to single-stream conventional nozzles, the multi-stream supersonic nozzle involves a larger number of design parameters and exhibits a strong interaction between the multiple streams. The serpentine configuration introduces a complex influence on the flow characteristics of the multi-stream supersonic nozzle, which presents significant challenges in designing high-performance nozzles. It is crucial to understand and effectively manage the flow features to optimize the design of multi-stream supersonic nozzles with a serpentine configuration. As a result, the effects of the serpentine configuration and nozzle pressure ratio (NPR) on the flow characteristics of the multi-stream supersonic nozzle were investigated numerically in this paper. The numerical simulation employs the implicit density-based algorithm and Shear Stress Transport k-ω turbulent model of the commercial software ANSYS Fluent. The results show that the shock waves and contra-rotating vortices are generated by the nonuniform main stream and corner vortices from the serpentine configuration when the streams mix, which lead to the decline of the aerodynamic performance compared to the no serpentine case. The mass flow rate of the main stream and tertiary stream reduce by 1.4 % and 4.2 %, respectively, and the thrust performance reduces by 0.35 %. As the NPR rises, the tertiary streams are compressed by the main stream. The mass flow rate of the tertiary streams drop sharply with the contraction of the actual throat area. The flow condition of the tertiary streams convert from the over-expanded condition of convergent-divergent nozzle to the critical condition of convergent nozzle. Due to the enlargement of the actual exit area for the main stream, the maximal thrust performance is at NPR = 7.0 instead of the designed NPR.

Experimental comparison of critical performance for variable geometry ejectors with different mixer structures

To further optimize the performance of Solar-driven Ejector Refrigeration system under variable driving conditions, ejectors design using conical-cylindrical mixers are more effective than using cylindrical mixers were elucidated. The effects of the nozzle exit position (NXP), area ratio (Ar), and expansion ratio (E) on the performance of the conical-cylindrical mixer ejector (CCME) and the cylindrical mixer ejector (CME) were investigated. It was revealed that compared with the performance of the CME at the optimal nozzle exit position, the variable geometry CCME exists a NXP range where both the critical entrainment ratio (Ercri) and critical compression ratio (Ccri) are larger. This NXP range can be widened by appropriately reducing the NXP or Ar of the CCME under a specified expansion ratio. Besides, under variable expansion ratios, the expansion ratio range in which both Ercri and Ccri of the CCME are better than those of the CME can be widened by appropriately reducing the NXP or Ar of the CCME. The results demonstrated that the CCME is more suitable for variable expansion ratios than the CME. This implies that using the variable geometry CCME has a higher energy utilization efficiency in a Solar-driven Ejector Refrigeration system than that of using the CME. This work provides a promising guide for achieving higher energy efficiency of an ejector refrigeration system under variable driving conditions.

Unsteady Reynolds-Averaged Navier–Stokes Simulations of a Ducted Wind Turbine

Abstract An unsteady Reynolds-averaged Navier–Stokes model on body-fitted meshes in a commercial package (SimericsMP+) with a mismatched grid interface is used to study fluid dynamics around a ducted wind turbine. The model is validated by studying turbulent flow past a marine propeller. The nondimensional thrust and torque coefficients are compared against experimental data and results from a large eddy simulation model. Both coefficients are found to be within 3% of experimental results. Following this validation, the impact of different tip speed ratios on the ducted wind turbine's fluid dynamics is assessed. The optimal tip speed ratio is found to be the design value of 3.93 with a maximum power coefficient of 0.465 based on the duct exit area. The corresponding thrust coefficient is found to be 1.02 based on the rotor area. Lower tip speed ratios experience larger flow separation on the duct interior. Higher tip speed ratios decrease the size of the low-velocity region behind the hub. The ducted wind turbine's performance at design conditions is compared to an open rotor. The ducted wind turbine increases the power coefficient by 96% over the open rotor. The impact of hub size on the ducted wind turbine is also studied by simulating a smaller hub with 77% diameter. At the design tip speed ratio, the smaller hub has a power coefficient of 0.417. The maximum power coefficient is found to be 0.446 at a higher tip speed ratio of 4.5.

Difference in perception-reaction time of plain and plateau drivers at expressway exit ramps

The low-pressure (and low-oxygen) environment in plateau regions significantly impacts the driver’s perception-reaction time (PRT) and, in turn, road safety. However, drivers faced increased workloads at interchange exit areas while the Tibet region experienced a significant improvement in high-grade highway construction. Therefore, this study aimed to quantitatively analyze the influence of the plateau environment on PRT. Using a UC/win-road simulator, 6 scenarios of expressway exit ramps were constructed. Then, a total of 50 participants (35 males, 15 females) in Nanjing (altitude of 50 m) and 50 participants (36 males, 14 females) in Lhasa (altitude of 3650 m) were recruited for the simulation experiments. The driver’s PRT was measured according to the visual fixation characteristics (using an eye-tracking device) and vehicle running data. The no-difference in PRT for various scenarios was validated using the one-way-ANOVA test. Then, the Spearman bivariate correlation and generalized linear regression model were used to analyze the influence of driver’s age, driving experience, gender, and acclimation period on PRT. In addition, the difference in PRT of different groups of plain and plateau drivers was further analyzed using the Mann-Whiteney U and Kruskal-Wallis tests. Although driving experience and gender affected the PRT of the plain and plateau drivers, the effect was greater in the plain areas. The low-pressure environment at high altitude had a more significant impact on young novice male drivers. These findings serve as valuable references for refining the design of expressway exit ramps and improving road safety in the plateau areas.

Origin of mysterious geothermal gas emissions in the middle of the Western Desert, stable shelf area, Dakhla Oasis, Egypt

This work responds to what was reported in various audio-visual media channels and to queries and explanations from individuals and local residents on the causes of gaseous and thermal emissions from the Earth near the vicinity of the village of Al-Hindaw in Dakhla city, New Valley Governorate, Egypt. At the location of the fume exit area, magnetic, seismic, and electromagnetic geophysical investigations were carried out to identify the factor(s) responsible for the event in question. Rock samples were collected and studied geochemically and radiographically to assess their chemical compositions, as well as the quantity of organic chemicals that may have contributed to the burning and temperature increase. In light of the results of the geochemical and geophysical research, it is believed that the self-ignitions are the result of near-surface reactions and oxidation instead of volcanic activity, such as the presence of magma or other comparable phenomena.

Visual Recognition Analysis of Optically Long Tunnels: Interaction of Dynamic Vision and Visual Perception

To understand the relation between the geometric design of optically long tunnels and visibility of the exit area, in this study oculomotor (eye movement) data are collected from several drivers in Yunnan Province, China, and drivers’ fixation rate and saccade amplitude in the visible zone of the tunnel are measured as key indicators. The driver’s visual recognition is analyzed and key elements in the optimal design of the exit points of optically long tunnels are discussed. The results show that visual recognition is closely associated with the radius of the road curvature: as the radius of curve decreases, the visual focus is gradually attracted to the inner side of the curve, the proportion of small-angle saccade increases, and the dispersion of the saccade amplitude decreases.

Optimizing the air flow pattern to improve the performance of the air-cooling lithium-ion battery pack

The change in the structure of the air-cooling battery thermal management system (BTMS) is demonstrated to improve its cooling performance. In previous research carried out by the authors investigating a 4 × 9 21,700 battery module, several exit areas close to the entrance area were designed and examined. The direction of the entrance area is perpendicular to the cooling channel, while the direction of the exit area is parallel to the cooling channel. A simulation analysis of the BTMS is carried out to optimize the cooling performance. It is found that with the gradual increase in the wind speed, the outlet position is gradually shifted towards the inlet area wall. This can maintain the average temperature, maximum temperature, and maximum temperature difference of the battery module at the lowest levels. The polynomial fitting method is used to establish the mathematical relationship between the distance from the center surface to the leftmost wall of the outlet area of the BTMS, the wind speed, and the main cooling index when the discharge rate is 2C. On this basis, the best fitting function is obtained, and the model is established for verification.The two BTMS models were validated at wind speeds of 8 m/s, and the average temperature of both BTMS was very close to the predicted value, with maximum deviations of 0.57 % and 1.01 %, respectively. This fitting method could help to design a better air-cooling BTMS.

Self-adaptive micro-hole breakout detection in the electrochemical discharge drilling process based on CNN-BiLSTM

Electrochemical discharge machining (ECDM) is an effective and promising technology for the micro-hole drilling of hard and brittle insulating materials such as glass, quartz and ceramics. Hole exit quality is an important part of through-hole machining quality in ECDM. The hole exit quality is influenced by two different machining states before and after the hole breakout. Therefore, it is necessary to identify hole breakout occurrence to provide a basis for achieving a machining strategy that matches the changing machining state and thus improves the hole exit quality. However, currently, there is no effective method to detect the hole breakout in the ECDM of micro-holes. In this paper, a self-adaptive micro-hole breakout detection method based on CNN- BiLSTM was proposed. The hole breakout detection can be expressed as a binary classification problem according to the analysis of the current signals collected before and after the hole breakout. The sufficiency of the raw current signal information was discussed. A CNN-BiLSTM model was established to detect hole breakout using the current signals as the training dataset. The CNN-BiLSTM model showed better performance compared to CNN, LSTM, BiLSTM and CNN-LSTM by comprehensive considering of accuracy, F1 score, AUC value, training time, predict time, breakout detection results and Dunn test results. Furthermore, the length of current signals used for each single detection and the threshold value used for breakout detection were discussed. An optimal threshold value was calculated, and the delay of detection was within 66 ms. The proposed method was successfully applied to the hole breakout detection in the through-hole drilling experiments and the success rate was 100 %. The hole exit area just after breakout were measured and compared to the hole exit area after hole completion, the average ratios of the former to the latter were 11.69 %, 27.29 %, 38.43 % and 44.41 % for the voltage of 39 V, 41 V, 43 V and 45 V respectively.

Cluster Analysis of Freeway Tunnel Length Based on Naturalistic Driving Safety and Comfort

The tunnel is an important component of freeway operation safety, and its classification method is the foundation of a refined management of operation safety. At present, the impact of different categories of tunnels on driver safety, comfort, and driving behavior under naturalistic driving conditions is not clear, and there is a lack of classification methods for tunnels of different lengths in their operation stages. This paper was based on the driving workload, which effectively expresses the safety and comfort of drivers. In this context, naturalistic driving experiments in 13 freeways and 98 tunnels with 36 participants were carried out. The DDTW+K-Means++ algorithm, which is suitable for drivers’ driving workload time series data, was used for a clustering analysis of the tunnels. According to the length of the tunnel, the operation-stage tunnels were divided into three categories: short tunnels (<450 m), general tunnels (450~4000 m), and long tunnels (>4000 m). The length of the tunnel had a positive correlation with the drivers’ driving workload, while there was a negative correlation with the vehicle running speed, and the range of changes in the drivers’ driving workload and operation safety risks in general tunnels and long tunnels was higher than that in short tunnels. Road and environmental conditions are important factors affecting the driving workload. The entrance area, the exit area of tunnels, and the middle area of long tunnels are high-risk sections in the affected area of the tunnel. These research results are of great significance for the operation safety management of freeway tunnels.

Compressor and Valve Control Performance Implications on Active Flow Control Aircraft

This study presents the feasibility of implementing commercial-off-the-shelf reciprocating piston compressors for a developed active flow control (AFC) actuation framework to quantify the aerospace relevant performance ramifications of control architecture and compressor operational choices. Three architectures are studied: supply valve metering, exit area metering, and a combined approach. All concepts are studied under varying compressor operation schedules. The analysis framework in this study integrates internal pneumatic actuation and discharge dynamics, an experimentally calibrated compressor pressure and thermal dynamics model, three feedback control architectures, and flight dynamics models. The framework is implemented in simulation to provide a user-friendly tool for linking AFC architecture choices to achievable flight trajectories. Actuator performance is evaluated using actuation time, output, compressor duty cycle, and specific energy consumption. Aircraft tracking performance is evaluated as usable time and slalom centerline deviation. The analysis indicates that a supply-volume-based metering approach is comparatively inefficient concerning an exit-area-based metering, resulting in high flight tracking error. Exit area metering provides the best efficiency and run time with some structural drawbacks, while the combined approach provides the best flight tracking performance at the expense of additional complexity. These results inform the choice of onboard AFC hardware choices.

Design Impacts on Ram Air Vane Cooling in an Ultra-Compact Combustor

Abstract The ultra-compact combustor (UCC) aims to decrease the length of gas turbine combustors using a unique design geometry which wraps a combustion chamber around the central axial flow. This distinctive design enables an out of the box type of cooling scheme to be investigated for the turbine inlet vanes, termed the hybrid guide vane (HGV) in the UCC. The leading edge of the HGV experiences only compressor exit air as combustion products do not interact with the vane upstream of the 14% axial chord location. Previous studies were conducted which computationally evaluated the viability of taking in freestream flow through the HGV stagnation region for use as coolant. Based on these studies, a six vane HGV was manufactured which incorporated a solid vane and five hollow vanes. Each of these vanes incorporated different features to vary the size of the internal plug, trailing edge exit, and film cooling holes. In the present study, the cooled HGV was experimentally analyzed using pressure, thermocouple, and infrared (IR) thermography measurements to evaluate internal coolant flowrates and pressure loss along with cooling performance. Furthermore, the vanes were compared to isolate the impact of design differences on vane cooling. It was found that the location of the internal plug and incorporation of film cooling holes had a minor impact on coolant flow and cooling. Additionally, results showed exit area had the largest impact on surface temperature and coolant mass flow where the largest exit area allowed less restricted coolant flow resulting in the lowest average surface temperature. However, completely blocking the exit slot forced coolant to exit only through film cooling holes, stagnating the majority of the internal flow, resulting in surface temperatures higher than the uncooled, solid vane.

Mikro-Frezeleme Yöntemi ile İşlenen İnce Duvarlı Yapılarda Deformasyonun İncelenmesi

Micro-thin-walled structures are frequently encountered in micro-pumps, micro-channel cooler plates, and micro-molds in the defense, aerospace and biomedical sectors. One of the micro-machining methods frequently used to obtain micro-thin-walled structures is micro-milling. The micro-milling method makes machining possible for micro-components with high accuracy and a good surface finish. However, there are many issues to consider when micro-milling thin-walled geometries. The fact that the wall deformation is directly related to the rate of progression necessitates knowing what effects the rate of progression cause on the wall deformation. Because the micro milling technique is generally used as the final cutting process in the creation of thin wall geometries in the industry. In this study, thin-walled structures were obtained by micro-milling the Al6061-T6 material. The influence of feed rate on wall deformation was investigated by applying different feed rates in micro milling experiments. Wall deformation measurements were performed using a motorized optical profilometer device. It has been observed that increasing feed value causes an enhance in cutting forces, it also causes an increase in the deformation of the micro-thin wall. The deformation distance between the end points of the micro-milled wall geometry using a feed rate of 1 µm/tooth is three times greater than the thin-wall geometry created using a feed rate of 0.2 µm/tooth. It has been determined that the deformation is much higher in the entrance and exit areas of the micro-thin wall. The wall deformation also decreases from the upper point to the lower points of the micro-thin wall. While the deviation distance in the measurement taken from the upper point of the wall geometry obtained by using the 1 µm/tooth feed rate, where the deformation is more, can reach 100 µm, the deviation at the lower point of the wall is negligible.

Geometric and non-geometric impact on Coanda effect propulsion device for UUV application

The present study investigated the effect of geometrical and non-geometrical parameters on the thrust performance of a pump-valve propulsion device consisting of a Coanda effect valve (CEV) and a pump. A more accurate theoretical model was also developed to predict the thrust of the pump-valve device. Firstly, a rough thrust model was developed based on existing theory to predict the thrust and energy loss generated by the pump-valve device under different exit and nozzle areas. Considering the limitations of the theoretical analysis, numerical simulations were carried out to evaluate the effect of various geometrical and non-geometrical parameters, including nozzle shape, nozzle area, control port width, exit area, inlet flow rate, etc., on the thrust performance of the CEV and the pump-valve device. Due to the margin between simulation thrusts and theoretical thrusts, we built an experimental platform and carried out relevant experiments. The experimental data verified the simulation results, and on this basis, the original thrust prediction model was corrected.