Conducting Model Tests Research Articles

Modeling of GPM and LPM in Centrifugal Pump for Obtaining Hydraulic Flow Pattern Types

The types of hydraulic flow patterns in laboratory testing through the use of physical modeling tools often encounter several challenges when confronted with the use of empirical model scales, namely, the issue of scale. Water structures in the horizontal dimension do not experience highly complex issues because there are many measuring instruments available, whether self-made, home industry-produced, or industrial-grade. The presence of water volume in storage can only be tested at a clear scale, especially when it is already within a water tower (reservoir) installation with a specific height. Determining the need for water storage in a water tower is not an easy task to calculate due to differences in height, diameter, and storage capacity. Hydraulic experts often overlook these differences, which can become a problem when there is a demand for the volume of water during peak flow conditions. The solution to this issue needs to be verified by conducting model tests using a device known as the Centrifugal Pump, which has not been previously explored for laboratory research. GPM LPM model tests on this device make use of instruments and numerous pressure measuring tools supplied with pressurized water by a pump at specific, measurable volumes. To analyze the flow rate, flow coefficients, flow velocity, Reynolds number, Froude number, and test results with various speeds (speed meter), researchers test and measure the capacity of GPM LPM for each valve opening, starting with openings of 0.5, 0.75, 1.00, reading the instruments, shifting the speed from 1, 2, 3, 4, up to the highest speed, which is 12. A graph is created to display the test results of the GPM LPM speed booster device, which contains an electric motor. The test is conducted with three repetitions for each valve opening, and the speed and travel time values from the instruments on the test device are recorded and mapped. Subsequently, the analysis results of the GPM LPM test are recommended to provide information to construction planners of water structures. These results show that, under specific conditions of different speeds and valve openings, there are variations in the volume and travel time values. This information can be applied to determine the required storage capacity for each water tower building with a hydraulic flow pattern based on Reynolds number (Re) and Froude number (Fr).

Validation of a numerical wave tank based on overset mesh for the wavestar-like wave energy converter in the South China Sea

The CFD-based numerical wave tanks (CNWTs) have become a valuable numerical tool for research and development (R＆D) of wave energy converters (WECs) with improvements in computational efficiency. Verification and validation are crucial during the development of a CNWT to demonstrate the precision of the numerical results. The CNWT was utilized to conduct model tests on a designed point-absorber wavestar-like WEC at a scale of 1:17.5. A model of the wavestar was tested at the physical wave tank (PWT) at the Tianjin Research Institute. Verification and validation investigations were carried out on the variation wave strategies of the CNWT, which involved test cases with varying wave encounter angles (WEAs), wave steepnesses (WSTs), and wave periods. The results indicate that the amplitude of the float motion response increased with the growth of the WEA, and the motion response of the model under WEA of 180 deg is 17.3 % larger than the 0 deg. The phenomenon of cut jet flow and gas-liquid mixing that occurred in both PWT and CNWT for sea states with larger WST. The detailed error and deviation analyses and frequency domain study of numerical and experimental results were conducted. The experimental measurements indicate that the numerical results for the motion displacement of the WEC and the free-surface elevation surrounding the WEC are in satisfactory agreement.

Investigating the influence of root layer quantity on the pullout bearing characteristics of root piles in coral sand foundations

Root piles with good load-bearing characteristics can be used as foundations for offshore wind power facilities. By conducting model tests on root piles with varying numbers of root layers in coral sand foundations and studying the theoretical pullout ultimate bearing capacity, the influence of the number of root layers on the pullout bearing characteristics of root piles is analyzed. Subsequently, a formula for calculating the pullout ultimate bearing capacity of root piles is derived, drawing on the Vesic foundation bearing capacity theory and the Rankine soil pressure theory. The results indicate that increasing the number of root layers enhances the ultimate bearing capacity of root piles, enabling them to better withstand pullout forces and control displacement. The axial force curve of the roots exhibits a step-like pattern. Additionally, the maximum lateral mechanical resistance of the root piles in 3 and 5 layers gradually shifts downwards with increased loading. While the total bearing capacity of the root section increases, the rate of increase diminishes over time. Model test data validates the proposed theoretical formula for calculating bearing capacity, affirming its reliability. These research findings furnish a theoretical groundwork for the practical application of root piles in engineering.

Concrete Carbonation of Deep Burial Storage Constructions under Model Aging Conditions

To ensure the safe operation of concrete structures of deep-burial storages, it is necessary to research the degradation mechanisms of such structures. Concrete carbonation is one of the key factors determining the service life of concrete structures. Existing methods for the concrete carbonation process research at various stages of the building structure life cycle make it possible to conduct model tests in the shortest possible time by simulating the operational factors influencing the corrosion process development. The authors carried out model tests of concrete of deep-burial storages using the method of accelerated concrete carbonation and by taking into account the effects of elevated temperatures. When exposed to elevated temperatures during carbonation, concrete samples exhibit a decrease in compressive strength in the first 56 days of testing by an average of 1.6 MPa. However, by the end of the tests (168 days), the strength of concrete samples at elevated temperatures is on average 4 MPa higher. The microstructure and carbonation dynamics were studied by XRD, TGA and SEM. The data obtained in the research can be used to develop models for predicting the service life of concrete structures of deep-burial storages.

Multiple earthquake-induced progressive failure of bedding slopes with a saturated weak layer: Shaking table model tests

The Longmenshan (LMS) orogenic belt located in the south-eastern Tibetan Plateau has suffered from frequent earthquakes. Despite the fact that multiple earthquakes can accelerate the catastrophic failure of deep-seated bedding landslides by causing rock mass damage accumulation, the seismic deformation evolution characteristics during the progressive failure have received limited attention. This study employs a physical model of deep-seated bedding landslides with a saturated weak layer as a slope prototype to conduct model tests that simulate the progressive failure induced by repeated earthquakes. Embedded sensors and digital image correlation (DIC) technology were used to monitor the seismic response and deformation evolution of the physical model. During the test, sensors embedded in the saturated weak layer recorded the excess pore water pressure (EPWP). The test results revealed that the EPWP responses are highly related to the input parameters of seismic waves and the seismic damage state of the weak layer. In addition, a deformation coefficient (Dc) was proposed to identify the deformation stages consisting of the release of steep tensile failure surface and the shear failure evolution from stable to accelerated deformation. Finally, the test results indicated that historical seismic damage accumulation will make an important contribution to later earthquake-induced coseismic instability, which provide new insight into the initiation of large landslides triggered by low magnitude earthquakes.

Experimental Study on Wave Current Characteristics and Stability of the Junction of Artificial Island and Subsea Tunnel

In order to ensure the safety and reliability of the submerged tunnel covering layer at the junction of an artificial island and tunnel under extremely bad conditions, the wave current characteristics and the stability of the protective structure in the variable slope section were studied. By conducting model tests, the coupling effect of wave and current is revealed in this study. The hydrodynamic field, including the varying angles between waves and currents, is simulated in the model test. The ratio (Hs′/Hs) of the wave height and the ratio (U′/U) of the velocity with and without the existence of a current, the relative velocity (U/C), the wave steepness (Hs/L), the relative water depth (d/L) and the angle (α) between wave and current are obtained, and the corresponding calculation expression is derived, by checking the test results, the empirical formula can better predict the changes of wave height and water flow after wave current coupling. The stable weight of the surface protection rock is obtained through an optimization test. Based on the relationship between the stable weight of the protection rock and the wave height under the wave–current coupling effect, a modified expression for calculating the stable weight of the armor block is derived. The modified calculation method can support estimating the stable weight of the armor rocks of an overburden structure of a similar immersed tunnel under the wave–current coupling effect. This study can not only solve the practical problems of major projects of the Shenzhen–Zhongshan channel but also provide valuable basic data and technical support for the construction of overburden of subsea-immersed tube tunnels in the future.

Morphological Evolution of Passive Soil Arch in Front of Horizontal Piles in Three Dimensions

The anti-slide pile is a primary method of landslide control. The effect of the passive soil arch in front of the embedded section of piles has a significant effect on the anti-slide pile’s bearing capacity. The upgraded model test scheme was used to conduct model tests with a pile spacing four times the width of the pile and a geometric scale ratio of 1:15. The anti-slide pile stress, pile bending strain, and soil stress in front of the pile were all studied in relation to the loading amount. In addition to the model test, the numerical simulation method was utilized to investigate the three-dimensional morphological change of the passive soil arch in front of the pile. The results indicated that: clearly, the side piles can eliminate the border effect. The distribution of pile bending strain along the pile after loading is referred to as a parabola. Bending failure occurred at a depth of 40 mm, approximately 0.9 m from the pile top. Under the condition that the pile spacing is four times the pile width, a passive soil arch occurs in front of the anti-slide pile’s fixed part, and its development can be split into four stages: formation, development, completion, and destruction. The passive soil arches in front of the piles are generated and destroyed gradually along the buried depth, and the three-dimensional surface of the space drops gradually along the buried depth with the loading amount and advances toward the loading direction until the anti-slide pile system fails. The research findings and experiences can serve as a basis for future research.

An experimental investigation on vortex-induced motion (VIM) of a tension leg platform in irregular waves combined with a uniform flow

Vortex-induced motion (VIM) of a tension leg platform (TLP) is critical to avoid structural and fatigue damages to the tendons and risers. Many previous studies have conducted model tests for TLPs in towing tanks. However, the models were usually established using linear springs to replicate the underwater moorings. In this study, a TLP model with full-water-depth tendons and top tension risers (TTRs) was developed. A series of model tests were conducted in a large-scale wave tank at three incidence angles (θ=0°, 22.5°, and 45°) for the reduced velocity ranging from 4 to 11.5 and two extra cases of flow combined with irregular waves. The maximum transverse amplitude of 0.32D was observed at a reduced velocity of 7.0 when θ=0°. On the other hand, the in-line and yaw motion experienced increasing amplitudes with reduced velocities and no lock-in region was identified. The most significant responses of transverse and yaw motion appeared at 0° and 22.5° headings, respectively, while no critical heading was recognized for surge motion. The competing mechanics between VIM and the wave-induced motion were revealed in the cases of combined flows and irregular waves. The tensions in tendons and TTRs that result from VIM were found as significant as those induced by wave loads, which highlights the necessity of considering VIM in the design of TLP. Furthermore, the result showed that the VIM amplitudes were considerably suppressed under the nonlinear stiffness and larger damping provided by the tendons and TTRs.

Effects of Locations of Spur Dyke on Bed and Scour around Bridge Piers in Meandering Channel

Spur dykes are the structures which are used to protect the eroding bank of rivers. They are sometimes also used to safeguard the life of many structures such as bridge piers, abutments etc. The efficiency of spur dykes has been checked in straight channels by conducting model tests in laboratories by many investigators. Very few studies were done in curved channels. In present work an attempt has been made to study the effect of location of spur dyke on bed and scour around bridge pier in curved open channel (bend angle = 80o ) with time. Experiment has been carried out in 80o channel bend at constant discharge (3.5×10–3 m3 /s) and bridge pier is located at angular displacement ϴ = 60o . Here ϴ is the angle the line drawn at the inlet of any bend to the line joining the centre of curvature and any point on the outer portion of the bend. It is found that maximum scouring occurs at ϴ = 0o and 20o along inner wall and at ϴ = 60o and 80o along outer wall. It is also found that scouring around bridge pier is more in the vicinity of pier and decreases with increase in distance from pier. The most suitable location for spur dyke to protect bridge pier is at angular displacement ϴ = 20o . Scour developed rapidly during initial time and then rate of scouring decreases with elapse of time.

Physical Model Test and Theoretical Study on the Bearing Behavior of Pile in Expansive Soil Subjected to Water Infiltration

Abstract A loading test device with infiltration function is developed to conduct model tests on the bearing behavior of single piles in expansive soil. The infiltration observation test and vertic...

МЕТОДИКА МОДЕЛИРОВАНИЯ ЯВЛЕНИЙ АЭРОУПРУГОСТИ

The material included in the article is a generalization of the authors ' experience in the field of setting and conducting model tests of building structures. An integral part of the experiment is the theory of physical modeling, which gives the correct approach to the formulation and conduct of experiments. The creation of construction structures of various classes and purposes is based on extensive preliminary research, among which, along with computational work, an important role is played by testing models of individual structural elements. In the article, based on the theory of physical modeling, the answer to two questions is given: - how to create a model, choose a real object (hanging mota); - how to recalculate the results of the experiment on the object under study.

Scale effect of rectangular and square footing of shallow foundation resting on cohesive soil

This experimental research work was performed to evaluate settlement and bearing capacity in cohesive soil. The predominant objective of this study is to develop the existing state of the knowledge about the present simulation processes to estimate its settlement and load carrying capacity. From the past literature study, the semi-empirical procedures were studied to estimate the settlement and bearing capacity parameters. The investigation was done into three parts, based on the past literature studies. The index and laboratory experimental investigations were done in the first stage. In the second part, the experimental procedure was elaborated to determine the settlement and load carrying capacity of small-scale model tests on cohesive soil. This research works presents, the effect of small-scale laboratory tests on the load carrying and settlement of model footings. The experiments were carried out with three types of model footing such as square, rectangular, and circular shapes were chosen to study the scale effect. For the circular footing, the diameters of 30, 40, and 50 mm sizes of plates were used and for square and rectangular model footings dimensions were used as 30mm×30 mm, 40mm ×40 mm, and 50mm ×50 mm and 50mm ×33 mm, 40mm ×28 mm, and 30mm ×20 mm respectively. A steel tank of size 330×220×300 mm was fabricated and used for conducting model tests. The width of the plates ranged from 50mm to 100mm for modeling plane strain and axisymmetric problems and care taken to avoid the wall friction when the load is applied. The size effects on settlement and bearing capacity was studied under different moisture conditions such as optimum moisture and plastic limit of the soil.

The Effect on Constant Heel on Circulation of a Vessel Calculated on the Basis of Investigations of M/S “Ziemia Zamojska” Model

Abstract The article presents modeling research on the M/S “Ziemia Zamojska” reduced model, carried out in an open fresh water area by a team of employees of the Department of Operating of Floating Vessels, Polish Naval Academy, Gdynia. The research involved circulating the model with constant angle of heel on the selected side, and the main engine set to full speed ahead. Using a real ship to carry this type of investigations is risky. It may lead to some failures like e.g. rudder failure, steering gear malfunction, overload and in some circumstances even main engine seizure. For this reason, ships are not tested with the rudder put to starboard or to port at the full speed ahead setting, even during a “Crash Stop” maneuver. However, based on the analysis of accidents at sea, and practical experience, it appears that during real operating conditions of vessels, there may occur situations when, for the sake of safety, the maneuver mentioned above must be carried out. Therefore, the authors had to conduct model tests of a floating vessel for the described case of ship operation

ПЕРСПЕКТИВНОСТЬ ПРИМЕНЕНИЯ РАЗЛИЧНЫХ КОММЕРЧЕСКИХ ПРЕПАРАТОВ ДЛЯ УСКОРЕНИЯ ПРОЦЕССА «СОЗРЕВАНИЯ» КУРИНОГО ПОМЕТА

In connection with the necessity to speed up the composting process and preserve the nutrients in chicken droppings, this paper considers the possibility of its processing with the help of the biologically active additive “Mefosfon”, the preparations “Gorynych”, “Tamir”, “Udachnuy”, “Doctor Robik” and hydrogen peroxide . The object of the study was the droppings-free chicken manure of the III danger class of “Yaratel’ poultry farm of “Ak Bars Poultry Production Company” branch. The experiments were carried out in the open air in 50 liter insulated polyethylene containers for 2/3 filled with chicken droppings for 45 days (July-August 2018). The doses of the drugs being applied were determined by the instructions for their use or by the results of previously conducted experiments. Control served as a litter without drugs. When conducting model tests, the temperature of the substrate was monitored, the smell level of the test substrate, the initial and final humidity of the chicken manure, the presence of pathogenic microflora in the resulting product were determined. Recycled chicken droppings in all experimental variants and control belonged to the IV class of danger to the environment. Microbiological analysis carried out at the end of the experiment showed that, in the variant containing “Mefosfon” preparation, the content of enterococci and coliform bacteria was the lowest and amounted to 4% and 2%, respectively, of the final content in the control samples, indicating the promise of using “Mefosfon” to reduce the time of maturation and neutralization of chicken manure.

The practical aspects of implementation of the thrust allocation procedure for a multi-propulsor underwater robot

Abstract This article addresses the practical aspects of the synthesis of an automatic control system for the thrust allocation strategy in the propulsion system of an unmanned underwater vehicle. The vehicle under consideration is a robot submarine equipped with a multi-propulsion system providing four degrees of freedom of movement. The power distribution algorithms are based on limited optimisation methods that allow the determination, on the basis of generalised torques and forces, of how much thrust is required to be produced by individual propulsors. Considering the issue of power distribution as a task of square and linear programming, two algorithms of thrust allocation were proposed and compared. The conducted model tests made it possible to evaluate their quality and efficiency in relation to speed and computational complexity.

Linear correlation constrained joint inversion using squared cosine similarity of regional residual model vectors

Inversion of geophysical data is inherently non-unique, so joint inversion has been used to reduce the ambiguity of inversion. Among other things, the coupling between different physical parameters is crucial in geophysical joint inversion. In this paper, we improve the coupling constraint based on ‘Squared Cosine Similarity’ of regional residual model vectors for joint inversion. Compared with the widely used coupling constraints in joint inversion, such as the cross-gradients constraint and the gradients dot product constraint, whose coupling are constructed by the computing of model parameter's gradient using ‘local’ adjacent grids to calculate the derivatives in specified directions, the ‘region’ of the new proposed constraint is defined as a specified model space in which two vectors to compute the dot product of cosine similarity should satisfied the condition they are linear correlated, because the constraint we designed is to force the value of squared cosine similarity in this ‘region’ tends to 1. If the condition is satisfied, the ‘region’ may be any size in the model space, i.e. the whole model space or small as the ‘local’ grids. As for the ‘residual model vector’, it means the difference between the inversed model parameter with the reference background models, and usually the background is taken as the initial model of inversion in the defined region, that is the uniform half space. As for the ‘squared’, it means no matter the regional residual vector's varying direction is same or opposite, the value of squared cosine similarity always tends to 1. Then we compute the squared cosine similarity from regional residual model vectors and constrain all the region's summed value to be 1 to enforce the linear correlation of regional model variations during joint optimization. So the proposed constraint will result in enforcing the correlation between regional model parameters’ variations. We conduct model tests with an application of seismic traveltimes and gravity anomaly to verify the proposed constraint in joint inversions, and we can see the improvement of the joint inversion over the results of separated inversions and cross-gradients or gradient dot product constrained joint inversion. We calculate the values of cross-gradients, dot product and the rock's physical relationship to prove that joint inversion with this new constraint can improve the linear correlation between velocity and density variations, avoid computing the model gradients of the adjacent ‘local’ grids and reduce the local discontinuities. We also test the proposed constraint on field data with gravity and magnetic anomaly in Lower Yangtze region, China, and the result reveals the consistency of high density and high magnetic basement.

3D Focused Inversion of Near-bottom Magnetic Data from Autonomous Underwater Vehicle in Rough Seas

The observation area of an autonomous underwater vehicle (AUV) often contains undulating terrain in which the shallow portions make a great contribution to near-bottom magnetic data. Magnetic information from varying terrain may be inadvertently removed when traditional topographic correction methods are used to reduce the effect of undulating terrain on inversion results. In this study, we introduce a terrain-weighting matrix into the focused inversion process to overcome this problem. To counteract the natural decay of the potential field, we used the focused inversion with a minimum support function to obtain focused results and depth-weighting function. We also used the interpolation-iteration method to mitigate the influence of the fluctuating observation surface on the inversion results. We verified the effectiveness of the proposed method by conducting model tests using near-bottom data measured along the Southwest Indian Ridge (SWIR) by the AUV, Qianlong II. We obtained the 3D magnetization structure of the oceanic core complex (OCC) area at the 28th segment along the SWIR and concluded that the OCC was primarily composed of gabbroic rock.

Laboratory Study on Response of Single Pile Adjacent to Supported Cut

This paper presents the response of single pile against excavation induced soil movement by conducting model tests at unit gravity. The study involves a series of tests conducted on piles of three L/d ratios 10, 20 and 30 embedded in medium dense sand. From the test results it was found that the pile head deflection and bending moment of pile decrease exponentially with increasing distance between the pile and the sheet pile wall supporting the excavation. Analyses of the test results show that the shorter passive pile (L/d = 10) deflects more when compared to a long pile (L/d = 30) and a point of contraflexure for a long pile occurs in the pile section approximately at a depth close to the depth of excavation. The influence of soil movement on the lateral response of pile is also analysed through 3-dimensional finite element analysis. The numerical results thus obtained are validated with the results of experiments. The Mohr–Coulomb material model adopted to represent the soil characteristics predicts the response of pile reasonably and compares well with the response observed in the 1g model test. Design charts are included to predict pile head deflection and maximum moment in pile for the excavation depth ratio (De/Lr) = 0.5. These charts can be adopted to predict prototype pile behaviour by applying scaling law of Wood (Geotechnical modelling, Spon Press, London, 2001). The results of numerical and 1g model tests are validated with the design methods of Chen and Poulos (J Geotech Geoenviron Eng 123(9):802–811, 1997) and Xu and Poulos (Comput Geotech 28:349–375, 2001) and the design charts proposed in this study for deflection of passive pile and sheet pile wall support system are validated with centrifuge test results of Leung et al. (J Geotech Geoenviron Eng ASCE 126(11):947–954, 2000).

Model tests and finite element analysis for the cyclic deformation process of suction anchors in soft clays

More attentions have been focused on the ultimate bearing capacity rather than the cyclic deformation process of suction anchors under cyclic loads in previous researches. Few researches are reported about the finite element analysis for the cyclic deformation process of suction anchors in soft clays, because lacking the suitable constitutive model that can not only describe reasonably the cyclic stress-strain responses of soft clays but also can be easily implemented into 3D nonlinear finite element analysis codes. The cyclic deformation process of suction anchor subjected to the combined static and cyclic loads are investigated by conducting model tests under 1 g condition, and the cyclic behaviors are simulated using the finite element method based on the UMAT subroutine for an elastoplastic bounding surface model proposed by the authors. The predictions show that the cyclic deformation process of suction anchor in soft clays can be simulated well by using the constitutive model and setting appropriate finite element calculation parameters. The cyclic displacement-time history and load-displacement response of the suction anchor can be predicted by the finite element analysis and the predictions are in good agreement with the test results. The failure modes of anchors can be predicted well because the predicted displacement components along vertical and horizontal directions are basically consistent with the experimental results. In addition, the cyclic bearing capacity of anchors can also be determined according to appropriate displacement failure criterion.

Experimental investigation of the uplift capacity of group anchor plates embedded in sand

In this study, the uplift capacity of anchor plates embedded in sand was investigated by conducting model tests. Square shaped anchors were used in the tests and parameters such as relative density of sand, embedment ratio (H/B), spacing ratio between anchors (S/B) and anchor configuration affecting the uplift capacity were investigated. Breakout factor and group efficiency which are dimensionless parameters were used to show the results. A series of finite element analyses and analytical solutions were additionally performed to ascertain the validity of the findings from the laboratory model tests and to supplement the results of the model tests. It can be concluded that the embedment depth in dense sand soil condition is the most important parameter with respect to the other parameters as to influencing the uplift capacity of group anchors.