Moment Coefficients Research Articles

Heliostat Wind Load Field Measurements at the University of Adelaide Atmospheric Boundary Layer Research Facility (ABLRF)

The University of Adelaide has recently commissioned a facility dedicated to investigating the atmospheric boundary layer (ABL) for the analysis of wind loads on full-scale heliostats. Wind tunnel testing is an affordable way to analyse loads on a scaled structure before committing to a full-scale design. Scale testing however has its challenges as most cases in literature fail to correctly scale the ABL when scaling a model due to the differences between the ratio of the heliostat chord to the boundary layer depth in a wind tunnel and ABL. There is a lack of direct comparison between wind tunnel and full-scale heliostat wind loads. The Atmospheric Boundary Layer Research Facility (ABLRF) consists of arrays of ultrasonic anemometers and a 1.5 aspect ratio heliostat, mounted on a 6-axis load cell, for the comparison of loads measured in the wind tunnel with a full-scale model. Preliminary results categorise the site to have a roughness of 0.01 m to 0.03 m indicating open country farmland, when compared to standards. Comparison between coefficients of lift force, drag force, and hinge moment on the heliostat model at a single elevation angle at the ABLRF and wind tunnel models in literature verify the commissioning of the site, allowing for further in-depth analysis of wind load coefficients at varying elevation and azimuth angles.

Aerodynamic and RSM Analysis of Wingsuit Stability

A Wingsuit is a Skydiving Jumpsuit that generates more lift for longer flights. This study examined the effects of side slip angles on a beginner wingsuit at 106 Reynolds number. Experimental tests were determined by using the length of the model scale at angles of attack ranging from 0° to 40° and sideslip angles of up to 20°. Force and moment coefficients were analyzed using variations in angles of attack and sideslip. Despite the absence of significant effects of sideslip angles on the lift and drag coefficients, side force and rolling/yawing moments were highly nonlinear. Flow structure visualization and numerical simulation show that surface stalls only occur on the lower side when slip angles are lower. In individual aviation sports, wingsuits are more advantageous when they have less sideslip. With Tuft visualization on the wingsuit model, the best aerodynamic coefficient under different flight conditions was determined by comparing the Response Surface Methodology performance under different flight conditions.

The Relationship between Balance Confidence and Center of Pressure in Lower-Limb Prosthesis Users

Background: Agreement between the activities-specific balance confidence scale (ABC) and center of pressure (CoP) in prosthesis users is still very much unknown. The purpose of this study was to investigate the agreement between ABC and CoP in lower-limb prosthesis users. Methods: Twenty-one individuals with lower-limb prostheses were recruited. Participants were provided with the ABC scale and performed static balance tasks during eyes opened (EO) and eyes closed (EC) conditions whilst standing on a force platform. Pearson product moment coefficients between CoP displacements and ABC scores were performed. Participants were also stratified by those who had better (≥80 on ABC scale) and less (<80 on ABC scale) perceived balance confidence. Displacement was compared using an independent t-test with Cohen’s d to estimate effect size with alpha set at 0.05 for these tests. Results: There was a significant inverse moderate relationship between eyes opened displacement (EOD) (18.3 ± 12.5 cm) and ABC (75.1 ± 18.3%), r = (19)−0.58, p = 0.006, as well as eyes closed displacement (ECD) (37.7 ± 22.1 cm) and ABC, r = (19)−0.56, p = 0.008. No significant difference in EOD (t(19) = 1.36, p = 0.189, d = 0.61) and ECD (t(19) = 1.47, p = 0.156, d = 0.66) was seen between those with greater and less balance confidence. Conclusions: Self-report and performance-based balance outcome measures are recommended when assessing lower-limb prostheses users.

Numerical study on aerodynamic characteristics of the grid fins with different grid patterns

Grid fins are unconventional control surfaces configured by a grid of cells within an outer frame; this grid acts as multiple lifting surfaces, and the pattern of the cells strongly affects the grid fin's performance. In this study, three-dimensional simulations were performed using a computational fluid dynamic approach with a k–ω shear stress transport turbulence model to investigate the effect of grid patterns on fin aerodynamic characteristics. Three fin models were designed, including square, tri, and hexa grid patterns, to be more independently comparative; other parameters consisting of the outer frame's dimensions, internal web's thickness, chord length, dragging area, and grid cell area were kept similar between the models. The Mach numbers 0.7, 1.2, and 2.5 corresponding to subsonic, transonic, and supersonic regimes were investigated for varying angles of attack from −5° to 15° for each fin model. The aerodynamic efficiency of grid fins is appreciably improved by increasing the normal force coefficient (CN) while reducing the area force coefficient (CA) and hinge moment coefficient (CHM). The results underscore the hexa grid pattern's superiority, with CN increasing by 2.2% and CA decreasing by 1.92% compared to the square model (the original model) at Mach number 0.7. Especially, the hexa model exhibited a substantial decrease in CHM, with the largest difference being 56.8% compared to the square model at Mach 2.5.

Numerical Simulation of Wind Load on Prefabricated Buildings Using Computational Fluid Dynamics

At present, the wind tunnel experiment is more and more widely used, but it is rarely used in the construction industry. Therefore, this thesis is to study the wind load of prefabricated buildings by numerical simulation. First, the application field of wind load numerical simulation is analyzed. Next, the numerical model is used to simulate the average wind pressure distribution on the building surface of single tower, tower G and tower F. The turbulence model is established based on fluid mechanics, which makes the obtained data more accurate and can converge quickly. Finally, the wind load interference effects of two fabricated towers and a single tower are analyzed. The experimental results show that the moment coefficient interference factor of tower F remains between 0.696~1.125 and that of tower G remains between 0.291~1.043. When the wind direction angle is 90°, the maximum values of the building base torque and the base bending moment around the X axis appear simultaneously, and the moment around the Y axis is not 0, which will change the stress of the building on the base. If the wind direction angle becomes 0°, the two fabricated towers will interact to reduce the impact on the base moment of the upstream building. Meanwhile, the wind pressure interference factor on the wall surface of prefabricated buildings remains between [-1, 1.5]. When the buildings in the upstream are blocked, the wind pressure interference factor may become 0. However, the shape coefficient of negative pressure on the inner wall of the building will increase rapidly due to the narrow channel effect. This thesis will analyze the wind load on the surface of prefabricated buildings through numerical simulation, which will help the wind engineering team build safer prefabricated buildings.

Hydrodynamic characteristics of an Asian sea bass-inspired underwater body

A novel underwater body geometry inspired from the morphology of Asian sea bass (Lates calcarifer) fish is developed, and its hydrodynamic coefficients for different combinations of angle of attack and drift angle are investigated using RANS-based CFD methods. The six degrees of freedom manoeuvring performance is evaluated by the calculation of surge, sway and heave forces and roll, pitch and yaw moments at Reynolds number 3.7 × 106. The numerical model is validated using experimental results for DARPA SUBOFF model. The sea bass sectional geometry has an inherent asymmetry about the horizontal plane, and this is observed in the force and moment coefficients. A detailed study for pressure coefficient and skin friction coefficient is presented, both along the length and circumferentially at specified locations for varying angles of attack and drift angles (-15° to 15°). Due to transverse pressure gradient, cross-flow structures are observed resulting in vortices from the mid-body that grow downstream, the strength depending on the angle of manoeuvre. It is observed that the sea bass-inspired body generates greater roll and pitch moments and heave force as compared to a symmetric tuna-inspired body for drift angles greater than 10°. The differences show the influence of asymmetry in underwater vessel geometry on its stability and performance during horizontal and vertical plane manoeuvres. The study of the hydrodynamic characteristics will aid the design of control surfaces and development of estimation of manoeuvring and propulsion performance for fish-inspired autonomous underwater vessels.

Airfoils optimization based on deep reinforcement learning to improve the aerodynamic performance of rotors

Airfoil optimization is the key to improving the aerodynamic performance of a rotor. However, conventional optimization approaches cannot modify the airfoil shape intelligently in the way that an aircraft designer would. Because the optimization process is largely uninterpretable and ungeneralizable, the optimization knowledge and experience cannot be extracted and applied to similar optimization tasks. To address these issues, we propose an optimization framework for rotor airfoils based on deep reinforcement learning (DRL). Our DRL-based framework is capable of learning an interpretable and generalizable optimization strategy for alleviating the dynamic stall of a rotor airfoil. First, to enhance the efficiency of airfoil dynamic stall optimization, a deep neural network is trained to predict the dynamic stall hysteresis loops of rotor airfoils as a surrogate model. The asynchronous advantage actor–critic reinforcement learning algorithm is employed to train and learn the optimization strategy for alleviating the dynamic stall of the rotor airfoil. Next, the OA212 rotor airfoil is optimized using the well-trained optimization strategy. The results show that the dynamic stall characteristics of the airfoil are improved after optimization. The lift coefficients of the optimized airfoil are significantly enhanced, and the drag and moment coefficients peaks are reduced by 46.3% and 73.8%, respectively, compared with the baseline airfoil. Then, 20 airfoils are optimized using the well-trained optimization strategy to evaluate the generalizability of the dynamic stall optimization strategy. The results demonstrate that the optimization strategy learned by DRL for the rotor airfoil optimization is generalizable. Finally, the numerical simulation results comparing a rotor with baseline airfoils to one with optimized airfoils demonstrate that the aerodynamic performance of the optimized rotor is superior to that of the baseline rotor.

Performance of a windsurfing sail under steady condition

This research investigates the aerodynamic forces and moments acting on a windsurfing sail during steady sailing. We performed wind tunnel experiments on a scaled-down sail model to measure the aerodynamic forces and moments at varying angles of attack and rig-back (swept-back). The study found that increasing the rig-back angle resulted in lower lift, drag, rolling moment coefficients and lift-to-drag ratio. Using kinematic considerations, the aerodynamic data was transformed into key performance parameters, including driving force, side force, and rolling moment. The study emphasis on the sail’s aerodynamic rolling moment by taking into account a maximum righting moment threshold from the sailor. This threshold can restrict the maximum achievable driving force from the sail, and is particularly important at high apparent wind speeds. The study suggests that higher rig-back angles can be beneficial when the maximum driving force is restricted by the moment threshold. In these conditions, the reduction in sail rolling moment from a higher rig-back angle can offset the potential reduction in lift-to-drag ratio. This finding provides valuable insights into the optimal techniques for improving windsurfing performance under steady sailing conditions. This study contributes to the understanding of the underlying physical principles governing windsurfing and provides a basis for further research in this area.

Pengaruh Lingkungan Sekolah Terhadap Hasil Belajar Siswa Pada Mata Pelajaran Pendidikan Agama Islam (PAI)

The school environment is the second major educational environment after family. Students, administrator teachers, counselors live together and carry out the educational process in an organized and planned manner. The problem examined in this study is how the influence of the environment situation of Pasundan 3 Cimahi Middle School on student learning outcomes in Islamic Religious Education subjects. The location in this study is Pasundan 3 Cimahi Middle School. The purpose of this study is to find out how much influence the school environment has on learning outcomes in Islamic Religious Education subjects. The sample in this study were 33 students from all students with details of 11 students from class VII, 11 students from class VIII and 11 students from class IX. To obtain valid data, researchers used data collection tools such as questionnaires, documentation and observation. As for data analysis, researchers used quantitative methods using statistical formulas namely Mean (average), Standard Deviation (SD), TSR, then product moment correlation and coefficient of determination. Based on the results of hypothesis testing that the school environment can influence student learning outcomes. This can be seen from the value of "r" of 0.539 with a significance level of 0.355 (5%) and 0.456 (1%). Thus the "r" count 0.539 is greater than the "r" table both at the significance of 5% and 1%. Then the calculation of the coefficient of determination obtained R2 0.290. Meaning 29% student learning outcomes are influenced by the school environment. So the alternative hypothesis Ha is accepted and Ho is rejected. This means that there is a significant influence between the school environment on student learning outcomes in Islamic Religious Education subjects at SMP Pasundan 3 Cimahi.

Estimation of Lower Limb Joint Angles and Joint Moments during Different Locomotive Activities Using the Inertial Measurement Units and a Hybrid Deep Learning Model.

Using inertial measurement units (IMUs) to estimate lower limb joint kinematics and kinetics can provide valuable information for disease diagnosis and rehabilitation assessment. To estimate gait parameters using IMUs, model-based filtering approaches have been proposed, such as the Kalman filter and complementary filter. However, these methods require special calibration and alignment of IMUs. The development of deep learning algorithms has facilitated the application of IMUs in biomechanics as it does not require particular calibration and alignment procedures of IMUs in use. To estimate hip/knee/ankle joint angles and moments in the sagittal plane, a subject-independent temporal convolutional neural network-bidirectional long short-term memory network (TCN-BiLSTM) model was proposed using three IMUs. A public benchmark dataset containing the most representative locomotive activities in daily life was used to train and evaluate the TCN-BiLSTM model. The mean Pearson correlation coefficient of joint angles and moments estimated by the proposed model reached 0.92 and 0.87, respectively. This indicates that the TCN-BiLSTM model can effectively estimate joint angles and moments in multiple scenarios, demonstrating its potential for application in clinical and daily life scenarios.

Wind tunnel testing of a Formula Student vehicle for checking CFD simulation trends

The aerodynamic performance analysis of Formula Student racecars has been mostly done by teams with CFD tools, for time and cost savings, that often lack proper validation. To address this, the FST Lisboa team performed a detailed wind tunnel (WT) test campaign, using a one-third scale model, under different configurations, including variable ride heights, bullhorn appendix, and rear wing flap settings, also replicated in CFD. The simulations used RANS with the SST k-omega turbulence model, with a 13.7 million polyhedral mesh for the test chamber region domain. Both experimental and numerical errors were estimated from the instrumentation and mesh convergence analysis, respectively. Comparisons were made between WT and CFD both in terms of local flow, using tufts for flow visualization, and global flow, using lift, drag, and pitching moment coefficients. Overall, the numerical streamlines agreed very well with the orientations of the tufts in experiments, but some discrepancies were found in regions of cross-flow and high-frequency unsteadiness, mainly caused by limitations of the visualization technique. The gamma transition model in CFD was abandoned as it could not replicate the WT observations. In terms of aerodynamic coefficients, a strong correlation was found between WT and CFD. The parametric studies revealed that the simulations captured the experimental sensitivity to each car setting parameter studied but the uncertainties did not enable a full quantitative evaluation of the aerodynamic performance. The drag reduction system significantly impacted the aerodynamic balance of the racecar, while the current bullhorn design proved to be ineffective. The ride height increase led to higher downforce, mostly due to the higher pitch angle of the vehicle, with negligible variation of the aerodynamic balance. This work validated the team CFD studies, building confidence in that trends estimated in numerical parametric studies are likely to be translated to the real prototype performance.

On the anti-rolling performance of a train using a vortex generator array

Vortex generators (VGs) have shown the potential to mitigate the train's operational instability issues caused by strong wind. Numerical simulations are used to predict the flow structures around a train with VGs of different heights. The improved delayed detached eddy simulation (IDDES) hybrid modeling method is adopted to predict the trailing vortices on the leeward field. The numerical method is validated by reproducing wind tunnel test results. The study results reveal that VGs are capable of reducing the rolling moment coefficient around the leeward rail of a train by about 5% ∼ 15% while keeping the drag of the train still lower than its operational drag without crosswind. The control mechanism lies on that the streamwise vortices generated by VGs are attracted to the large-scale trailing vortices, resulting in the pressure on the leeward wall rising. The differences in the domain frequencies between VGs and Baseline cases in POD modes indicate that the VGs changed the periodicity and symmetry of the vorticity fluctuation. This study provides a new method to improve the safety of trains under crosswinds.

Exploring the Relationship between Principal Leadership Styles and Teacher Work Discipline

This research explores the relationship between the school principal's leadership style and teachers' work discipline in State Senior High Schools Pekanbaru, Riau. The study adopts a quantitative approach with a survey method and correlation technique. Through random sampling, the research involves 40 teachers from eleven State Senior High Schools in Pekanbaru. Data collection is conducted using a questionnaire, which has been calibrated with validity testing using Pearson Product Moment and reliability coefficient with Cronbach's Alpha formula. The research results indicate a relationship between the leadership style of school principals and the discipline of teachers in State Senior High Schools in Pekanbaru. The significance testing of a correlation coefficient of 0.51 supports this relationship. It suggests a moderate connection between the principal's leadership style and teacher discipline. This study implies that enhancing teacher discipline can be achieved through the role of the school principal's leadership style. In other words, a correlation of 0.51 indicates that the principal's role in leading and guiding teachers can have a positive impact on their work discipline, and these efforts may be crucial in achieving a higher quality of education.

Modeling the Motion of an Elongated Contour under Free Surface of a Heavy Fluid under Large Froude Numbers

The flow around an elongated smooth contour under the free surface of a fluid is considered. The fluid is perfect, incompressible, and heavy. The critical flow branching and flow shedding points are located on the contour. The depth of the contour immersion and its length are given. It is assumed that the velocity magnitude on the free surface is close to its value in the undisturbed flow. A nonlinear approximation of the Bernoulli integral on the free surface associated with logarithm is used. Two auxiliary planes in which the flow domain is a half-plane with an excluded circle and an annular region are used. The complex potential is determined in the first parametric plane using a conformal mapping onto the annular region. A system of equations is derived for finding the defining parameters. This system is solved using the minimization of a functional and an iteration method over two sets of parameters. An algorithm and computer program for solving this system are developed. The hydrodynamic characteristics of a specific hydrofoil are computed. Results for the coefficients of wave drag, lift force, moment, and position of the contour center are analyzed depending on the Froude number and circulation of different signs. Examples of computations of nonlinear waves formed on the free surface at significant Froude numbers are given.

Bearing capacity of UHPC‐NC connection structure in negative moment zone of PC beam bridges

AbstractA new type of UHPC‐NC (normal concrete) structure in the negative moment zone was proposed to improve the bearing capacity of the connection structure in the negative moment zone of prefabricated prestressed concrete (PC) beam bridges. First, the distribution characteristics of the crack, cracking load, ultimate moment, and ductility coefficient of the new structure were obtained by the 1:4 scale model tests. The feasibility of the connection structure is verified. Then, the value ranges of critical structural parameters affecting the bearing capacity of the connection structure based on the plane section assumption analysis, including the reasonable thickness of the UHPC layer, the reinforcement ratio of the longitudinal tensile reinforcement, and the diameter of the reinforcement, are obtained. At the same time, based on the verification of the finite element model, the influence of crucial research parameters on the bending capacity of the connection structure is obtained by using the finite element method. Finally, a theoretical method for the bending moment capacity of the connection structure of the UHPC‐NC structure is proposed, considering the high ductility characteristics of UHPC materials. The average relative error between the calculation results and the finite element method is within 7.2%, which verifies the reliability of the calculation method in this paper and provides a reference for its design and engineering application.

Experimental Study on Wind Load and Wind-Induced Interference Effect of Three High-Rise Buildings

Wind loads of high-rise buildings are a key parameter in architectural design. The magnitude and distribution characteristics of wind loads are of great importance for the safety and economy of structural design. The wind loads of high-rise buildings are quite different from those of monomer buildings. The wind-induced interference effect could significantly increase the local wind pressure of buildings, causing potential safety hazards for the main structure and enclosure structure. For the three common high-rise buildings, we adopted the wind tunnel test method to measure the surface pressure of each building. The corresponding Re number was 8.2×106. This paper studied the shape coefficients, fluctuating wind pressure coefficients and base bending moment coefficient of each building with different wind direction angles and different spacing ratios, and the maximum value of each parameter and the corresponding working condition were statistically analyzed. The results showed that, under any wind direction angle, the fluctuating wind pressure coefficients on all sides of the building were affected by the spacing ratio, and the fluctuation range was large. When the wind angle was 180º, the fluctuating wind pressure coefficients on the sides of Building 1 were most affected by the slope ratio. At this wind angle, the maximum value was 0.43 at a slope ratio of 5.0, which was 65% different from the minimum. Partition shape coefficients of some sides and top surfaces changed significantly with the spacing ratio. When the spacing ratio was 5.0, the base bending moment coefficients in the downwind and crosswind directions reached their maximum values, and the wind direction angles where the maximum values of the base bending moment coefficients in the downwind direction were 40º and 50º, respectively, and the wind direction angle where the maximum value of the base bending moment coefficients in the crosswind direction was 10º. Due to the influence of the wind angle and the building spacing ratio, the wind loads on the facades of the pyramidal group of buildings varied greatly, and the wind-induced interference effect was evident. The wind load between the building facades in the three buildings was different, and the wind disturbance effect was evident. Therefore, the most unfavorable stress state and interference state of the structure should be comprehensively considered in the wind resistance design of the three buildings. The building spacing ratio should preferably be set to 3.0, and wind angles of 10º, 40º, and 50º should be avoided whenever possible.

Experimental studies of airliner aerodynamic characteristics at overcritical angles of attack

PurposeThe main purpose of this study was to determine the basic aerodynamic characteristics of the airliner Tu-154M at the wide range of the overcritical angles of attack and sideslip angles, i.e. α = −900° ÷ 900° and β = −900° ÷ 900°.Design/methodology/approachWind tunnel tests of the Tu-154M aircraft model at the scale 1:20 were performed in a low-speed wind tunnel T-3 by using a six-component internal aerodynamic balance. Several model configurations were also investigated.FindingsThe results of the presented studies showed that at the wide range of the overcritical angles of attack and sideslip angles, i.e. α = −900° ÷ 900° and β = −900° ÷ 900°, the Tu-154M aircraft flap deflection affected the values of the drag and lift coefficients and generally had no major effect on the values of the side force and pitching moment coefficients.Research limitations/implicationsThe model vibration which was the result of flow separation at high angles of attack was the wind tunnel test limitation.Practical implicationsStudies of the airliner aerodynamic characteristics at the wide range of the overcritical angles of attack and sideslip angles allow assessment of the aircraft aerodynamic properties during possible unexpected situations when the passenger aircraft is found to have gone beyond the conventional flight envelope.Social implicationsThere are no social implications of this study to report.Originality/valueThe presented wind tunnel test results of the airliner aerodynamic characteristics at overcritical angles of attack and sideslip angles is an original contribution to the existing not-too-extensive database available in the literature.

Parenting Styles as a Predictor of Substance Abuse among Undergraduates in Public Universities in Kwara State

The study aimed at viewing Parenting Styles as a predictor of substance abuse among undergraduates in Nigeria and also determined the relationship between the independent and dependent variables. Descriptive research design of correlational type was used for this study. A sampling procedure was employed to select 216 respondents and a questionnaire consisting of two sub-scales namely; Substance Abuse Scale (SAS) and Parenting Practices Questionnaire (PPQ) were adapted as the research tool for the collection of data. Frequency counts, percentage and charts were used to describe demographic data of sampled respondents while the research hypothesis was tested at 0.05 level of significance with the use of Pearson Product Moment Coefficient (PPMC). The findings showed that majority of undergraduates in public universities in Kwara State were affected by the authoritarian parenting style which instigated most of them to become substance addicts. Suggestions and recommendations were made to parents, counselors, lecturers, University management, government and religious groups among which is the organisation of self-awareness skills training by the counsellors and excursion exercise to rehab centers by the management as well as provision of spiritual counseling by the religious groups. Suggestions were made to further this study for wider scope and efficient results in the society.

Influence of swirl and ingress on windage losses in a low-pressure turbine stator-well cavity

As part of the drive towards achieving net-zero flight by 2050, the development of ultra-high bypass ratio engines will place greater importance on the efficiency of the low-pressure turbine. Stator-well cavities can be a significant source of loss within this system, primarily due to the ingestion of annulus air, which can rotate at a speed less than that of the disc. This paper presents the results of a joint experimental/numerical campaign to relate windage torque to the flow physics in a scaled, engine-realistic stator-well geometry with superposed flows. The primary variables were the pressure ratio across the stator row and the swirl ratio at inlet to the cavity. This is the first paper to relate simultaneous torque and swirl measurements in a stator-well cavity. The numerical simulations have also provided insight into the fluid dynamic behaviour. A reduction in cavity windage torque with superposed flow rate was shown, consistent with the increase in swirl measured by experiments and predicted by computations. The pre-swirled superposed flows reduce the ingestion of negatively swirling fluid from the annulus, effectively increasing the swirl ratio of the flow in the cavity towards that of the rotor. This reduces windage losses; at the design condition with superposed flow, the cavity windage torque reduced by 60% of that of the reference case. Sealing effectiveness increased with superposed flow rate. This was demonstrated through gas concentration measurement/simulations, a reduced radial flow velocity into the cavity and a reduced mass flow rate across the interstage seal. The application of a turbulent transport model showed that ingestion could be explained by shear-driven diffusion. Ingestion increased as inlet swirl ratio reduced, while the pressure ratio was found to have a negligible influence on windage moment coefficient, swirl ratio and sealing effectiveness. In addition to providing fluid dynamic insight, the gas concentration results can be used for validating thermomechanical models. The results in this paper will be of practical interest to the engine designer who wishes to scale information to engine-operating conditions.

ANALYTICAL SUBSTANTIATION OF DETERMINATION OF INTEGRAL CHARACTERISTICS OF ROTOR SYSTEMS OF URBAN CRANES

The work is devoted to the actual problem of analytical substantiation of determination of integral characteristics of rotor systems of city-building cranes, knowledge of which is necessary for carrying out further balancing of their rotors on coasting (or in the process of start-up). It allows to refuse the use of contact vibration sensors and other special equipment for monitoring the balancing process. Besides, there is a possibility to optimize the driving torque (during start-up) and braking torque during coasting of the rotor system. The purpose of the work is to develop an algorithm for determining the integral characteristics of the rotor system at start-up/run-out at a special ratio of moment coefficients - components of the total moment of resistance to rotation. Approaches and models of mathematical physics and classical calculus of variations are used. The results obtained in the paper will be useful for clarification and improvement of engineering methods of calculation of rotor systems of construction/urban cranes operating in transient modes (start-up, coasting, reversing, etc.), both at the stages of their design and in the modes of real operation.