Hydrodynamic Impact Research Articles

Hydrodynamic impact and power production of tidal turbines in a storm surge barrier

To estimate the impact on energy production and environment of tidal turbines placed in the Eastern Scheldt Storm Surge Barrier a Computational Fluid Dynamics (CFD) study has been carried out on the additional head differences induced by the turbines. The CFD model focusses on a single gate opening of the Storm Surge Barrier and includes half of the adjoining gates on either side. In this 40 m wide Gate a 1.2 MW array existing of five Tocardo T2 tidal turbines has been installed as part of a demonstration project in 2015. Transient computations of the barrier with and without the turbine array were carried out for a range of quasi stationary tidal phases. The turbines are resolved in detail as rotating equipment: real-time rotation of the turbine blades (involving the displacement of the mesh nodes in an unsteady setting) is implemented, and torque and thrust for the prescribed speed of rotation is provided as output. The results for velocity, power and thrust are compared with field experiments to validate the model. Based on these computations an estimate of the effect of turbines on the discharge capacity of the storm surge barrier is given. This information will be used to parameterize the tidal turbines in the far-field hydrodynamic model of Eastern Scheldt estuary for the ultimate assessment of the effect of tidal turbines on energy production and on the environment.

Hydraulic Tests of the Operational Spillway of the Bureya Hydraulic Project

The results of hydraulic tests of the operational spillway of the Bureya Hydraulic Project in 2008, 2009, and 2016 are presented. The tests were intended to assess the geometric parameters of the downstream flow, the aeration and spray conditions, the hydrodynamic impact on the main gates, and the flow and wave pattern downstream between HWL = 248.30 m and TCS = 256.00 m.

EXPERIMENTAL STUDIES OF THE INFLUENCE OF WAVES ON THE BREAKWATER OF A PARTIAL VERTICAL PROFILE

Abstract. The article is devoted to the issues of physical experimental researches connected with the determination of the parameters of wave quenching when overflowing them through the superstructure of enclosing hydraulic structures (ENS) of incomplete vertical profile. The research was conducted in the hydrowave laboratory of the Department of Hydraulic Engineering of the Odessa State Academy of Civil Engineering and Architecture. The article presents partial results of experiments performed on ENS of incomplete vertical profile. The models were made on a geometric scale and were subjected to wave effects similar to the conditions of the natural section of the coast of the Odessa Bay in compliance with the criteria of similarity. The construction of new structures of enclosing hydraulic structures requires careful primary experimental research. These researches mostly often carried out on physical models in specialized hydrowave laboratories, allow to get rid of risks of financial losses at the wrong choice of types and elements of the designed objects. The carried out researches allow estimating with a high degree of reliability, according to scale conditions, physics of the processes proceeding on models which will also be observed at the operation of real construction. The physics of the process of hydrodynamic impact on hydraulic structures is often difficult to describe only with the help of a mathematical model, which confirms the high degree of importance of physical experiments. The progress of technical science largely depends on the ability to make more accurate measurements. High-precision measuring equipment was used in laboratory tests. This paper describes the method of conducting experiments that were performed on one physical model, under three different conditions of the location of the superstructure relative to the quiet level, as well as different values of the initial wave heights. The use of structures of incomplete vertical profile, in order to protect the waters of seaports, as well as elements of the coastal infrastructure of maritime cities will increase economic attractiveness by reducing financial costs, thanks to the reduction of the topside of the enclosing structures.

Numerical simulation on the mechanical properties of marine float

As the key structure of buoyancy and dynamic lift generation, the float is one of the most important attachments of the fishing gear in ocean fishery. For the special work environment, the float may deform and move under the hydrodynamic force when it works. At the same time, the motion may cause the impacting action from fluid and structures around. Then the investigation of the mechanical behavior of the float is of important significance for the structural design and performance optimization of the fishing gear, and even for the development of the ocean fishery. The three-dimensional numerical model of marine float working in the flow field was established based on the Computational Fluid Dynamics (CFD) method and the finite element (FEM) method according to the structural form and the mechanical characteristics in operation. The hydrodynamic performance and impact resistance were analyzed, and the response mechanism of float structure under the action of hydrodynamic load and impact load was summarized. It aims at providing basic theory support for the structure design and optimization of marine float and the related fishing gear.

The role of hydrodynamic impact force in subaerial boulder transport by tsunami—Experimental evidence and revision of boulder transport equation

The hydrodynamic impact contributes to the initiation of subaerial boulder transport by tsunamis and tsunami-like flows. Here, we consider two approaches to modelling this impact force—hydrostatic and hydrodynamic—and assess the suitability of each in boulder transport models. The model proposed, solved as an ordinary differential equation, eliminates the need to assume a conservative value of flow acceleration. Introducing the hydrodynamic impact force reduces, by almost 45%, the recognised overestimation of threshold flow velocity in simple hydrodynamic models for boulder transport. By contrast, including the hydrostatic impact force reduces the overestimation by less than 10%. We found the new model consistent with the results of simple flume experiments. In these experiments, three rectangular limestone blocks of 27–70 cm3 in subaerial pre-transport setting condition were subjected to tsunami-like flow by sudden opening of a sluice gate.

Optimization design of a honeycomb-hole submarine pipeline under a hydrodynamic landslide impact

Submarine pipelines are likely to be impacted by frequently catastrophic landslides, resulting in broken pipelines and causing irreversible economic losses; however, because pipelines located in deep-sea environments are simply laid atop the seabed, effective protective measures have not yet been proposed. In this paper, a pipeline with a uniform distribution of honeycomb holes on the surface, namely, a honeycomb-hole submarine pipeline, is discussed and optimized in detail. A computational fluid dynamics (CFD) approach is verified and improved several times and then applied to conduct 120 numerical simulations for 12 types of suspended submarine pipelines under 10 conditions covering the Reynolds number range required by the project conditions. First, the typical characteristics of the impact forces acting on pipelines in a seawater environment are systematically investigated, and the peak drag force is isolated as the most dangerous load caused by a landslide impact. Second, according to the formation and reduction mechanism of the drag force, it is proposed that a honeycomb-hole submarine pipeline can effectively delay the separation of the boundary layer, reduce the impact velocity, prolong the arrival time, and decrease the differential pressure drag force. Finally, two normalized parameters, the depth ratio and area ratio, are established to develop an optimization design methodology, and the optimal design values of honeycomb-hole pipelines are achieved under the support of limited data. This work presents a protective technology for submarine pipelines and provides new insights into the response of fluid-structure interactions.

Hydrodynamic effect on non‐stationary vehicles at varying Froude numbers under subcritical flows on flat roadways

AbstractWater is essentially a powerful component, strong enough to even move vehicles at the lowest hydraulic parameters. The flow orientation as well as the geometric and physical characteristics of a vehicle attribute to the way floodwaters affect and control the vehicle. Herein an effort has been made to study the hydrodynamic impact on a non‐stationary vehicle partially submerged attempting to cross a flooded roadway (flat conditions). In arriving at the outcomes, extensive experimental testing was carried out on a Malaysian made city car, Perodua Viva (1:10), which was controlled to be partially submerged under the influence of subcritical flows. The experimental data was proven through theoretical equations based on the instability failure modes. The variation of the Froude number with respect to varying hydrodynamic forces has been further explored and conversed. The incipient velocity formulation proposed herein has been validated through the experimental data and the results showed good agreement between the two with a correlation coefficient ofR2= 0.85. Among the main findings, it was noticed that the buoyancy force governed vehicle weight at depths greater than and equal to 0.0457 m for the scaled model. On the other hand, below critical depth, the dominancy of the drag force over frictional resistance and driving force caused sliding instability.

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

The hydrodynamic loads of a disk impacting pure and aerated water are investigated experimentally and numerically. Experiments are performed on a rigid disk with different aeration levels and focus on the spatial and temporal pressure distribution. Drop tests are conducted by a specially designed apparatus to prevent the variation of velocity during the slamming period. A specially designed bubble generator, able to adjust the void fraction, is utilized to generate uniform and tiny bubbles. A high-speed camera is utilized to record the water spray and splash curtain. A homemade compressible multiphase solver based on the reduced five equation model is adopted to evaluate the impact loads, which assumes the water and bubbles sharing the same velocity and pressure. The results show that bubbles in the water have a significant influence on the impact loads. As the void fraction increases from zero to nearly 1%, the peak impact pressure is reduced considerably and the impact duration is becoming obviously longer. In aerated water impact, the disk has a more uniform pressure distribution on the surface. However, the pressure impulse in aerated impact tests is basically unchanged compared with that in pure water.

Hydrodynamic benefits of artificial cilia distribution towards photodegradation processes

Nature has devised unique ciliary arrangements among organisms towards efficient flow manipulation around their respective environments. The hydrodynamic impact of various ciliary arrangements is yet to be fully understood. In this aspect, this study was designed to elucidate the hydrodynamic benefits of ciliary arrangements towards the photodegradation process. In particular, the hydrodynamics impact of artificial cilia distributed uniformly line by line arrangement and in a circular ring arrangement were studied within the microfluidic environment with a specific aim to achieve efficient photocatalytic applications. It was observed that when the artificial cilia were arranged in circles, the average photodegradation capability of device was accounted as high as 72 % at the end of a 25-minute cycle which is 20 % improvement compared to the traditional line by line arrangement. The comprehensively hydrodynamic analysis further suggested that artificial cilia arranged in a circular ring form can generate the collaboratively secondary flow rotation as quantified in vorticity magnitude which is absent in its counterpart design. These secondary flows enhanced mixing in the microfluidic network which significantly improved the photodegradation efficacy. This acquired knowledge can be further implemented towards designing an efficient microreactor for identifying next-generation photocatalytic materials.

Spreading and bouncing of liquid alkane droplets upon impacting on a heated surface

This paper reports an experimental investigation on the impact dynamics of liquid normal alkane (n-heptane, n-decane and n-tetradecane) droplets on a stainless steel surface using high speed photography and long distance microscopic techniques. Particular interest is paid to comprehensively explore the effects of liquid viscosity and surface roughness on droplet spreading and bouncing dynamics at different thermal hydrodynamic impact regions. Specifically, firstly, high speed images identified four regimes (evaporation, nucleate boiling, transition boiling and film boiling regime) of physical phenomena that couple the droplet spreading hydrodynamics, heat transfer and phase change. Bubbles generation due to the heating of the surface with compression of air disk under the droplet was observed and this phenomenon is firstly promoted and then inhibited with the increase of the wall temperature until finally no bubbles were observed when wall temperature is beyond the Leidenfrost point (TL). Rim disturbances during spreading were observed at relatively high Weber number with wall temperature higher than TL. Increasing wall temperature reduces the rim disturbance. Secondly, the measured non-dimensional maximum spreading diameter βmax decreases with the increase of surface temperature until it becomes a constant when temperature is beyond TL. Rough surface was found to have a lower TL because of larger vapor pressure provided by more nucleation sites. Finally, for wall temperature beyond TL, droplet bounces up after a certain period of residence time (τr). It takes more time for droplet to rebound at larger We because of larger βmax takes longer time to retract and rebound. Both surface roughness and liquid viscosity showed no influence on time to reach βmax (τmax), but significantly increases τr by slowing the retracting process, which both should be considered in future model of τr.

Experimental and numerical study of the water entry of projectiles at high oblique entry speed

The water entry of cylindrical projectiles at high oblique speed has been investigated experimentally and numerically. Projectiles with three types of noses and different lengths are tested. The projectiles are lunched at different angles, and the development of supercavities are recorded using high-speed camera. During the water entry, deflections occur due to the deviation of the initial velocity and/or the hydrodynamic impact force. The evolution of the supercavities of projectile without deviation is observed. It is found that the collapse of cavity and the generation of new cavity occur alternatively. The motion and the evolution of supercavities at the initial stage of the water entry are simulated through computational fluid dynamics, the typical pressure distributions have been analysed. The drag coefficients are dominated by the nose shape.

Modelling the impact of tidal range energy on species communities

Tidal energy has the potential to form a key component of the energy production in a number of countries, including the UK. Nonetheless, the deployment of tidal energy systems is associated with potential environmental impacts as prime resource sites often coincide with unique ecosystems inhabited by sensitive organisms. Previous studies have generally focused on the hydrodynamic impact of tidal energy schemes, i.e. how schemes alter the flow dynamics and sedimentary transport processes. Whilst these efforts are key in understanding environmental impacts, there is no straightforward step for translating sediment to faunal changes. Species distribution models offer methods to quantitatively predict certain possible impacts of tidal energy extraction. The River Severn is a distinguished candidate region for tidal energy in the UK featuring sites under stringent ecological protection regulations. We examine the impact of a proposed Severn tidal barrage on 14 species via the linking of hydrodynamic modelling to species distribution models. Through a selection of species that are linked via a simple food web system we extrapolate changes in prey species to the respective predator species. We show that species at lower trophic levels would be adversely affected by the barrage, but higher trophic level organisms increase in possible habitable area. Once food web relationships are acknowledged this increase in habitat area decreases, but is still net positive. Overall, all 14 species were affected, with most gaining in distribution area, and only four losing distribution area within the Severn Estuary. We conclude that a large-scale tidal barrage may have detrimental and complex impacts on species distribution, altering food web dynamics and altering food availability in the Severn Estuary. The methodology outlined herein can be transferred to the assessment and optimisation of prospective projects globally to aide in the sustainable introduction of the technology.

Hydrodynamics of a Rising Oil Droplet With Bacterial Extracellular Polymeric Substance (EPS) Streamers Using a Microfluidic Microcosm

During the Deepwater Horizon oil spill, the unprecedented injection of millions of liters of chemical dispersant at the wellhead generated large quantities of submillimeter oil droplets that became entrained in a deep sea plume. The unexpected generation of these droplets has resulted in many studies in the last decade aiming to understand their transport and fate during and after the spill. Complicating matters, the plume coincided with a microbial bloom, and in addition to ocean dynamics these droplets were subjected to biological processes such as biodegradation and microbial aggregation. A lack of field observations and laboratory experiments using relevant conditions has left our understanding of these biotic processes and the role they played in the fate of the oil droplets poorly constrained. Furthermore, while biodegradation has been incorporated into drop transport models using available data, the effects of microbial aggregation involving extracellular polymeric substances (EPS) on their transport has seldom been incorporated into modeling efforts particularly due to our lack knowledge of these processes. We use a microfluidic platform to observe a bacterial suspension interacting with a 240 μm oil drop in conditions relevant to the drop rising through the microbial bloom. We observe the development of individual, practically invisible bacterial EPS threads extending from the drop surface which can capture additional passing bacteria and form bacteria-EPS aggregates. Using high speed imaging, we make high resolution flow measurements both with and without EPS threads present and analyze a momentum balance to elucidate the hydrodynamic impact of these threads. Surprisingly, these thin individual EPS threads cause a significant disturbance in the pressure field around the drop which in turn increases the drag which would drastically reduce the drops rising velocity in the water column. We demonstrate that this mechanism which plausibly occurred in the deep sea plume would have major impacts on both the drop and bacteria transport during and after the Deepwater Horizon oil spill.

A new physically based impact model for debris flow

A new analytical model is proposed to estimate the peak impact pressure of debris flow exerted on a rigid barrier. The new model consists of two terms, p = α1ρ0gh0 + 0·5ρ0u02, accounting for static and dynamic impacting effects, respectively. The static coefficient α1 is determined according to equations governing the mass and momentum conservation and energy conservation, and the dynamic coefficient 0·5 is adopted on the basis of the Bernoulli equation. The new analytical model is validated for a wide range of Froude number (Fr) with data collected from past studies on small-scale experiments and field observations and numerical simulations of debris flow as a particle–fluid mixture performed by coupled computational fluid dynamics–discrete-element method (CFD–DEM, for wide-range coverage of Fr). Based on equivalence with the new model, the empirical coefficients involved in conventional pure hydrostatic (k) and pure hydrodynamic (α) impact models are found positively and negatively correlated to Fr, respectively. A unique relationship between k and α is further derived: (cos θ/k) + (1/α) = 1, where θ denotes slope angle. The underlying physics of this relationship is interpreted. According to the proposed model, a design chart in terms of Fr is further recommended for practical design of debris-resisting barriers. The new analytical model offers a possible improvement on robust and reliable estimation of debris flow impact on a rigid barrier.

Effects of hydrodynamic impact on water from the viewpoint of cluster theory. Surface tension

Variation of surface tension coefficient σ of distilled water under high-energy impact (hydrodynamic cavitation) was studied by the ring separation method. Force impacts on surface tension of water have been studied experimentally. Conditions have been found under which the surface tension coefficient σ decreases to 20%. The paper explains the produced results on the basis of cluster theory of water structure. The experimentally produced relaxation time of the surface tension of cavitation-activated distilled water to initial value has been found to be 3.5 hours.

Designing In-Seam Gas Drainage Technology Based on Hydrodynamic Approach

The article presents science based technological solutions that are essential for the development of the country’s coal mining industry in terms of ensuring safety and efficiency of underground coal mining on the basis of improving in-seam gas drainage technologies using hydrodynamic impact on coal seams. Experimental work on the in-situ testing and approval of the new holistic technology was successfully done in the production panels 24-58, 24-58, 24-60 and 24-62 at the Kirova mine. That included underground hydrofracture of the working seam carried out from the development headings. High effectiveness of the proposed in-seam gas drainage technology was confirmed by effective methane extraction from the working coal seam, reduction of gas content in longwall faces and significant cut-down of equipment nonproductive time in areas covered by active in-seam gas drainage.

Numerical evaluation of the hydrodynamic impact characteristics of the air launched AUV upon water entry

In this paper, water entry process of air launched AUV is investigated by employing fully coupled finite element method and arbitrary Lagrange–Euler formulation (FEM-ALE) and using penalty coupling technique. Numerical model is established to describe the hydrodynamic characteristics and flow patterns of a high-speed water entry AUV. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments of the earlier study. Selection of suitable advection method and mesh convergence study is carried out during experimental validation process. It is found that appropriate mesh size of impact domain is crucial for numerical simulations and second-order Van Leer advection method is more appropriate for high speed water entry problems. Subsequently, the arbitrary Lagrange–Euler (ALE) algorithm is used to describe the variation laws of the impact load characteristics with water entry velocities, water entry angles and different AUV masses. Dimensionless impact coefficient of AUV at different velocities calculated using ALE method is compared with SPH results. This reveals that ALE method can also simulate the water entry process accurately with less computational cost. This research work can provide beneficial reference information for structure design of AUV and for selection of the water entry parameters.

Hydrodynamic impact on trace metals in sediments in the cascade reservoirs, North China.

Cascade reservoirs facilitate the effective use of water resources and help to alleviate existing problems of water shortage in drought-prone regions. However, the geochemical behavior and controlling mechanisms of trace metals in response to the operation of cascade reservoirs are relatively unknown. Here, trace metals (As, Cr, Cu, Li, Ni, Pb and Zn) from thirty sediment cores from cascade reservoirs (Panjiakou and Daheiting Reservoirs) in China were evaluated. Multiple methods including geochemical baseline, geostatistical analysis, factor analysis (FA), and positive matrix factorization (PMF), were combined to assess pollution status, identify and quantify potential anthropogenic sources, and determine the influence of hydrodynamic conditions on trace metals distribution. The results indicate that minor enrichment of trace metals appeared in both cascade reservoirs. However, trace metal concentrations exhibited spatial heterogeneity between two cascade reservoirs, and diverse hotspots of different metals were unexpectedly observed. This can be explained by the following three aspects: (1) Metal hotspots were detected upstream of the cascade dams via geostatistical analysis and FA, particularly for naturally sourced metals (As and Li) where dam interception resulted in higher concentrations in the upstream reservoir. (2) PMF analysis identified agricultural, industrial, and natural sources to account for 23.44%, 41.61%, and 34.95%, respectively, to the metal concentrations in the downstream reservoir. Anthropogenic emissions were the dominant factors influencing the spatial variability of Cu, Pb, and Zn between the cascade reservoirs, with higher concentrations observed in the downstream reservoir. (3) The hydrological regime also influenced the redistribution of human-derived metals, where slower flow velocities at river bends resulted in higher deposition of metal-bearing particles. This study shed light on the spatial distribution of trace metals in response to the construction and operation of cascade reservoirs, and it suggests that trace metal hotspots should be monitored to prevent potential contamination in sediments.

Effect of moisture conditioning on mechanical and healing properties of inductive asphalt concrete

The objective of this paper was to study the effect of hydrodynamic impact on durability and healing performance of inductive asphalt concrete (IAC) through moisture induced sensitivity test (MIST). AC-13 inductive asphalt concrete containing steel fiber was designed and Marshall specimens were prepared to suffer MIST in orthogonal condition. After MIST, cutting was performed to observe the corrosion of steel fibers inside while semi-circular bending (SCB) test was conducted to evaluate the mechanical properties. Then fracture-healing procedure was carried out to investigate the strength recovery ratios of the specimens before and after MIST. Meanwhile, the crack healing ratio and change of air voids inside asphalt concrete were observed by computed tomography (CT) scan test. The results showed that there was no corrosion of steel fibers inside samples after short term simulation in the laboratory. The tensile strength and fracture energy decreased after MIST. The changing trends of strength recovery ratio and fracture energy recovery ratio were consistent with that of tensile strength. CT-scan indicated that the healing ratio of crack was up to 92.3%. The initial air void content of asphalt concrete was 4.7%, 5.7% after adding steel fibers, and 4.87% after induction heating. However, the air void changed from 5.7% to 6.8% after MIST. Orthogonal test factor analysis showed that temperature was the most significant factor affecting the durability of asphalt concrete during MIST.

Evaluation of dynamic impact of flow with bridge pier using smoothed particle hydrodynamics method

This paper presents a numerical model for the hydrodynamic impact of water flow with a bridge pier placed on a group of piles using the smoothed particle hydrodynamics (SPH) method. A new boundary processing technique using a combination of ghost particles and dynamic boundary particles is implemented in the SPH simulations of this study. The numerical probes are uniformly distributed over the vertical surface of the structure in order to obtain detailed measurements of the flow pressure on the structure over time. Using the SPH simulations, the velocity field of the unstable flow surrounding the piles and the equivalent hydrodynamic force acting on the pile cap are determined. The vulnerable impact locations on the structure surface are also predicted from the time-pressure histories. Additionally, the predicted hydrodynamic pressure values are compared with those proposed by AASHTO (2012) for bridge design considerations.