Zhiguo He

• Professor
• Director at Zhejiang University

The three-equation model (TEM) was developed in the 1980s to model turbidity currents (TCs) and has been widely used ever since. However, its physical justification was questioned because self-accelerating TCs simulated with the steady TEM seemed to violate the turbulent kinetic energy balance. This violation was considered as a result of very stro...

The hydrodynamics of a two-vent turbulent forced plume propagating in a linear stratification has been studied by a series of laboratory experiments using the two-tank method and the Particle Image Velocimetry (PIV) technique. The velocity fields and turbulence characteristics of a two-vent plume under different source buoyancy flux, ambient strati...

Plain Language Summary Motion for mineral particles driven by hydrothermal plumes in the deep ocean is not well understood due to the complex environment involving a nonuniform background and ocean currents. To characterize particle trajectories and corresponding sediment distribution, we trace mineral particles using specialized computer code and...

Particle-laden gravity currents down a slope in stratified fluid are important processes in lake, estuary, and ocean environments. By conducting direct numerical simulations, this study investigates the detailed dynamic features of lock-exchange particle-laden gravity currents down a slope in linearly stratified environments. The front velocity, se...

Empowered by the combustion‐enabled transient driving method (TDM), underwater soft robots exhibit instantaneous high‐speed leaps from water, presenting valuable applications in robotic engineering. This study delves into the optimization of hydrodynamics during the high‐speed jumping through the water‐air interface, aiming to improve the overall p...

This study presents a comprehensive investigation into the dynamic behavior of particles with varying diameters transported by horizontal buoyant jets in linearly stratified fluids. An advanced modeling approach is developed that utilizes the realizable k-ε model based on Reynolds-averaged navier–stokes equations for buoyant jets mixing with strati...

The equations of motion of a continuous fluid and rigid, non-Brownian particles that interact through contacts are averaged to derive average balance equations. The averaging procedure is generic, requiring only linearity and commutation with the space and time derivatives. No assumptions about the fluid's rheology and the particles' shapes and com...

We report on chute measurements of the free-surface velocity $v$ in dense flows of spheres and diverse sands and spheres-sand mixtures down rough inclines. These and previous measurements are inconsistent with standard flow rules, in which the Froude number $v/\sqrt{gh}$ scales linearly with $h/h_s$ or $(\tan\theta/\mu_r)^2h/h_s$, where $\mu_r$ is...

This chapter presents important experimental and numerical findings regarding the dynamics of gravity currents in various stratified environments. First, the macro- and microstructure of gravity currents descending an inclined bed in linearly stratified environments were studied using high-speed camcorders and particle image velocimetry technology....

The collision and interactions between counterflowing density currents frequently occur in nature and engineering practices along the coastal regions. However, the mechanisms and implications of these interactions remain an active research area. In this study, we developed a high-resolution numerical model to simulate the hydrodynamic characteristi...

The combustion actuation method opens a unique pathway for high-performance soft robots, allowing for high accelerations in multifunctional applications. Along with multifunctionality come great challenges in effective robot structure design, accurate control and prediction of combustion-actuated motions, and practical implementation of various app...

As climate change continues to worsen, coastal areas are increasingly vulnerable to more frequent and severe storm surges. This poses a significant risk to economic entities, particularly in areas that have undergone rapid development. However, quantitative assessment of economic losses from storm surge disasters in China has been challenging due t...

Tidal flat plays an important role in coastal development because of its ecological and spatial resources. We take the southern tidal flat in the macro-tidal turbid Hangzhou Bay as an example to study the long-term (1990–2020) evolution of the muddy tidal flat, using remote sensing data and field observational data. The detailed bathymetric elevati...

In this paper, the simultaneous effects of boundary roughness and upslope on lock-release gravity currents were investigated by laboratory experiments, focusing on current propagation, entrainment processes, local vorticity fields, and velocity profiles. Based on the depth-averaged momentum equation, a new theoretical model that predicts the curren...

Active hydrothermal vents provide the surrounding submarine environment with substantial amounts of matter and energy, thus serving as important habitats for diverse megabenthic communities in the deep ocean and constituting a unique, highly productive chemosynthetic ecosystem on Earth. Vent-endemic biological communities gather near the venting si...

Autonomous underwater vehicles have been extensively developed in the past decades and deployed for various ocean research activities. While the leaping‐out motions of underwater creatures have motivated the development of underwater robots with the motion ability to jump out of water, the dynamics of such jumping robots have not been fully describ...

Time-resolved particle image velocimetry (PIV) experiments and direct numerical simulations (DNS) were conducted to study colliding gravity currents. This aimed at understanding the complex collision dynamics, quantifying important collision parameters, and obtaining high-resolution velocity fields of the interaction processes. The novelty of our c...

In the stratified environment, systematic experiments are carried out to understand the impacts of rigid vegetation on the evolution of lock-release gravity currents, including the propagation process and entrainment characteristics. A theoretical model is developed to predict the gravity currents completely entering the vegetation-drag-dominated r...

Storm surge, a major disaster in coastal areas, is generated by tropical cyclones, particularly hurricanes. Strong currents and waves during storm surges often cause sediment transport and beach erosion, significantly damaging the coastal ecosystem. This paper presents a flow-wave-sediment-morphodynamic coupled model to predict morphodynamic change...

There has been a growing need for soft robots operating various force-sensitive tasks due to their environmental adaptability, satisfactory controllability, and nonlinear mobility unique from rigid robots. It is of desire to further study the system instability and strongly nonlinear interaction phenomenon that are the main influence factors to the...

Systematical downslope‐turbidity‐current experiments were performed to clarify the relationship between sediment‐transport modes and current propagation patterns caused by rigid vegetation, as well as adjustments in turbulence characteristics of current. The equations for predicting the front velocities of downslope turbidity currents with emergent...

Underwater minirobots have attracted significant interest due to their value in complex application scenarios. Typical underwater minirobots are driven mainly by a soft or rigid actuator. However, soft actuation is currently facing challenges, including inadequate motional control accuracy and the lack of a continuous and steady driving force, whil...

Storm surge-induced flooding (SSIF) is a major hazard for coastal areas under intensified typhoons. Therefore, it is essential to assess the potential impacts of SSIF (SSPIA). This study proposes a multidisciplinary framework for refined SSPIA using an ocean model and a refined exposure estimation method. First, a finite-volume coastal ocean model...

It has been a great challenge to develop robots that are able to perform complex movement patterns with high speed and, simultaneously, high accuracy. Copepods are animals found in freshwater and saltwater habitats that can have extremely fast escape responses when a predator is sensed by performing explosive curved jumps. In this study, we present...

We conduct three-dimensional direct numerical simulations to investigate the mixing, entrainment and energy budgets of gravity currents emerging from two-layer stratified locks. Depending on the density and layer thickness ratios, we find that either the upper layer or lower layer fluid can propagate faster, and that the density structure of the ov...

The unabated flooding and erosion of mudflats at the low-lying Nigerian Transgressive Mahin coast require prompt measures to forestall further damage/attacks on shorelines and adjacent communities. However, a proper understanding of the mudflat subsurface materials is key for the successful design of a sustainable protection measure in this section...

Soft robotics has opened a unique path to flexibility and environmental adaptability, learning from nature and reproducing biological behaviors. Nature implies answers for how to apply robots to real life. To find out how we learn from creatures to design and apply soft robots, in this Review, we propose a classification method to summarize soft ro...

Underwater vehicles have opened a unique path to multifunctionality and environmental adaptability. However, inadequate studies have been conducted to investigate the dynamic principle and performance of underwater vehicles in real applications with complex external conditions. Here, we propose a type of combustion‐enabled underwater vehicles that...

It has been a great challenge to develop robots that are able to perform complex movement patterns with high speed and, simultaneously, high accuracy. Copepods are animals found in freshwater and saltwater habitats that can have extremely fast escape responses when a predator is sensed by performing explosive curved jumps. Here, we present a design...

Immiscible contaminants are commonly involved in naturally occurring suspensions. The resulting variations of their flow behavior has rarely been evaluated. Here, we investigate the variation of the viscosity of the oil-based two-phase suspension over a period of two years, which is exposed to the ambient air at the production stage. We find that t...

Immiscible contaminants are commonly involved in naturally occurring suspensions. The resulting variations of their flow behavior has rarely been evaluated. Here, we investigate the variation of the viscosity of the oil-based two-phase suspension over a period of two years, which is exposed to the ambient air at the production stage. We find that t...

This study experimentally investigated the impacts of rough and porous (RP) bed and sedimentation processes on the coherent structures, turbulence intermittency, and anisotropy of saline and turbidity currents. Results reveal that the local current concentration responds immediately (saline current) or languidly (turbidity current) to turbulence bu...

In this study, repeated lock-exchange experiments under well-controlled conditions were carried out to evaluate the uncertainty of the macro-propagation and entrainment process and the statistical variation/correlation of the current parameters. The results show that the lobe and cleft structures grow in amplitude while short in wavelength as curre...

In this study, repeated lock-exchange experiments under well-controlled conditions were carried out to evaluate the uncertainty of the macro-propagation and entrainment process and the statistical variation/correlation of the current parameters. The results show that the lobe and cleft structures grow in amplitude while short in wavelength as curre...

Hydrodynamics plays a significant role in the underwater motions, environmental disturbances, and kinematic characteristics of autonomous underwater vehicles (AUVs). However, the added mass coefficient has typically not been considered in analyzing the underwater motions of AUVs. Here is report the combustion actuated autonomous underwater vehicles...

Bridge health monitoring system can play a role in bridge safety early warning, fatigue diagnosis, and life prediction. However, traditional bridge health monitoring system relies on manpower or battery power supply, which challenges the real-time effectiveness of health monitoring sensors. Herein, we proposed a self-powered bridge health monitorin...

Underwater vehicles play important roles in underwater observation, ocean resource exploration, and sample collection. Soft robots are a unique type of underwater vehicles due to their good environmental adaptability and motion flexibility, although they are weak in terms of actuation and response ability. The transient driving method (TDM) was dev...

Soft robotics has opened a unique path to flexibility and environmental adaptability, learning from nature and reproducing biological behaviors. Nature implies answers for how to apply robots to real life. To find out how we learn from creatures to design and apply soft robots, in this Review, we propose a classification method to summarize soft ro...

The rheological properties of natural mud are closely related to nautical depth estimation, wave propagation, and morphology evolution of muddy coast. In this study, the rheological properties of the natural mud collected from Luxi Island and Zhoushan Island in China were investigated. Shear stresses in steady state or oscillatory state were impose...

Understanding the marine hydro-thermohaline environment is essential for terrestrial meteorology and the coastal ecosystem. Here, we provide insight into the hydro-thermohaline environment at the Qiongdongnan continental slope of the northern South China Sea and the mechanism controlling it, with focus on its short-term characteristics. We employ a...

Typhoons are extreme weather events that cause serious social and economic losses in coastal and estuarine areas worldwide. Understanding the impact of typhoons on sediment dynamics is essential for protecting coastal areas from these marine disasters. Hangzhou Bay is macro-tidal, turbid, and frequently affected by strong typhoons. In this study, w...

Sediment hyperpycnal flow is one of the most important processes for mass transport, which is essential to coastal morphodynamics. Herein, we studied the generation and maintenance of the sediment hyperpycnal flow in the Yellow River Estuary (YRE) using a three-dimensional finite volume coastal ocean model (FVCOM). The model considered the effect o...

The combustion-enabled transient driving method (TDM) has been proposed to improve the payloads and response-ability of soft actuators. However, given the extremely rapid (~9 ms) and forceful (>600 N) phenomenon, TDM leads to challenges in quantitatively investigating the combustion-soft membrane interaction and predicting the corresponding thrust...

Typhoon-induced storm tides can cause serious coastal disasters and considerable economic losses. Understanding the mechanisms controlling storm surges helps the prevention of coastal disasters. Hangzhou Bay (HZB), a typical macro-tidal estuary, is located on the east coast of China, where typhoons frequently occur. The funnel-shaped topography mak...

We investigate the submerged collapse of weakly polydisperse, loosely packed cohesive granular columns, as a function of aspect ratio and cohesive force strength, via grain-resolving direct numerical simulations. The cohesive forces act to prevent the detachment of individual particles from the main body of the collapsing column, reduce its front v...

A series of constant-flux saline and turbidity current experiments were carried out, focusing on the coupling impact of bed roughness and permeability on current propagation, mixing, and turbulence characteristics. The distinct current propagation phases on RI (rough and impermeable) and RP (rough and permeable) beds are identified respectively. Ex...

In this paper, fluid-particle interactions in lock-exchange turbidity currents (TCs) over a flat bed are investigated using a model combining LES and DEM (Large-Eddy Simulation and Discrete Element Method). The reliability of this model is demonstrated via comparing the numerical solutions with measurements of the front positions, fluid velocity pr...

Integrated structural health monitoring (SHM) uses the mechanism analysis, monitoring technology and data analytics to diagnose the classification, location and significance of structural situations (e.g., sudden or cumulative damages) to ensure the functionality and operation of bridges. Integrated SHM systems have improved the maintenance, manage...

In this paper, fluid-particle interactions in lock-exchange turbidity currents (TCs) over a flat bed are investigated using a model combining LES and DEM (Large-Eddy Simulation and Discrete Element Method). The reliability of this model is demonstrated via comparing the numerical solutions with measurements of the front positions, fluid velocity pr...

This paper presents a GPU (Graphics Processing Unit)-accelerated and LTS (Local-time-Step)-based finite volume Shallow Water Model (SWM). The model performance is compared against the other five model versions (Single CPU versions with/without LTS, Multi-CPU versions with/without LTS, and a GPU version) by simulating three flow scenarios: an ideali...

Freshwater plume at the Changjiang River (CR) mouth are essential to the coastal water quality and ecosystem because they can cause estuary stratification and hypoxia, potentially deteriorating the water environment. Furthermore, the advection heat transport is modulated by increasing anthropogenic effects. A comprehensive understanding of the infl...

Cohesive sediments in coastal zones and estuarine mudflats have transport mechanisms that are not well understood due to the complex sediment properties that influence their erodibility. However, understanding coastal sediment composition and behaviour is important to determine its resistance to hydrodynamic forcing. This study investigates the pro...

Horizontal buoyant jets in stratified fluids are investigated by employing a computational fluid dynamic model validated by experimental data. The characteristics of time mean flow, turbulence, and entrainment are quantified. We observed that turbulence parameters such as the turbulent kinetic energy, the turbulence dissipation rate, and turbulent...

Typhoon Mangkhut, in 2018, was one of the worst typhoons in recent history that has made landfall in the Pearl River Estuary (PRE) China. It swept along the coast of Guangdong Province, causing severe damage to many areas and affecting more than one million people. To study the hydrodynamics and sediment dynamics in different sub-regions of the PRE...

Field investigations were conducted to study the seasonal variation of hydrodynamics and sediment transport in Indus River Estuary (IRE), Pakistan. The data of water levels, currents, salinity, and suspended sediment concentration (SSC) were collected hourly covering both wet and dry seasons. Tidal amplitudes were higher near the mouth than those a...

Particle-laden gravity currents propagating in stratified environments, such as turbidity currents induced by floods in estuaries or triggered by landslides in oceans, are important and complicated geophysical processes that require multidisciplinary studies. This paper numerically investigates the dynamic features of lock-release particle-laden gr...

Changjiang River Estuary (CRE), as one of the largest fluvial estuarine systems worldwide, experiences great changes in river discharges, sediment loads and geomorphology, due to heavy anthropogenic activities. The contribution of sediments to stratification in CRE was examined by analyzing the field data of sea surface level, current, salinity, su...

Typhoon-induced intense rainfall and urban flooding have endangered the city of Zhoushan every year, urging efficient and accurate flooding prediction. Here, two models (the classical shallow water model that approximates complex buildings by locally refined meshes, and the porous shallow water model that adopts the concept of porosity) are develop...

Deep-sea hydrothermal plumes are an essential medium for exchanging the heat and elements between the lithosphere and hydrosphere and contribute to elemental cycling and marine chemistry evolution. In this paper, based on field video footage of a black smoker recorded at the Wocan-1 hydrothermal field on the slow-spreading Carlsberg Ridge in the no...

In this study, we develop the mechanical metamaterial-enabled piezoelectric nanogenerators in the gyro-structure, which is reported as a novel green energy solution to generate electrical power under quasi-static excitations (i.e., <1 Hz) such as in the ocean environment. The plate-like mechanical metamaterials are designed with a hexagonal corruga...

In this paper, a computationally efficient shallow water model is developed for sediment transport in the Yangtze Estuary by considering mixed cohesive and non-cohesive sediment transport. It is firstly shown that the model is capable of reproducing tidal-hydrodynamics in the estuarine region. Secondly, it is demonstrated that the observed temporal...

While fluvial flows carrying relatively coarse sediments involve strong two-phase interactions, existing numerical modeling in the field-scale is mostly based on quasi-single phase flow model. Here a computationally efficient two-phase hydro-sediment-morphodynamic model is developed with a special focus on field applications. The hybrid LTS/GMaTS m...

Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind‐blown) and plays a key role in shaping sedimentary landscapes of planetary bo...

Horizontal warm buoyant jets injecting into a linearly stratified ambience are common in lakes, estuaries, and oceans. Dynamic features and potential surface temperature signatures of heated buoyant jets are experimentally investigated using particle image velocimetry and an infrared camera. Results reveal that when heated jets are completely under...

A series of lock-release experiments are carried out to investigate the hydrodynamics of weakly and strongly stratified two-layer gravity currents (GC) on a flat bottom. A particle image velocimetry (PIV) system combined with an optical method is used to obtain the mixing process, front velocity, and velocity profiles of the two-layer GCs, focusing...

The large variations in salinity at the salinity maximum in the northern South China Sea (NSCS), as an indicator for the changes in the Kuroshio intrusion (KI), play an important role in the hydrological cycle. The high salinity here is more than 34.65 at the salinity maximum and is intriguing. In the past, the salinity was difficult to trace in th...

Coastal reclamation projects have been extensively constructed along the coastline of the East China Sea over the past decades. To investigate the impact of reclamations on the Rui’an coastal zone, regional tidal and sediment dynamics were studied by combining field data and numerical modeling. Field data of tidal elevation and currents, suspended...

Predicting the consequences of colliding gravity currents remains one of the most significant challenges in geophysical fluid dynamics. While the collision phenomenon has long been established through field observations, irregular natural occurrence and measurement limitations denied a comprehensive quantitative analysis of its dynamics. Herein, we...

Based on FVCOM hydrodynamic numerical model and coastline topographic data in 2013, a three-dimensional numerical model of fine sediment transport in Hangzhou Bay has been established to explore the water and sediment exchange mechanism between Hangzhou Bay and the open sea at different typical sections. The results of validation with measured and...

Previous investigations regarding river bifurcation mainly focus on the conditions of a stable bifurcation and how key factors affect the asymmetrical features of a bifurcation. In this paper, a numerical case study is presented of the 2012–2014 north to south shift in the Sanba mid‐channel bar of the Taipingkou waterway's dominant branch in the Ya...

Soft robots have been widely studied to accomplish multifunctional on-land tasks in recent years. Here, we develop a type of combustion-enabled soft jumpers that are able to move through multiphase media (e.g. water–air multiphase) with a high-speed of ∼6 times body length per second on average and up to ∼9 times body length per second at most whil...

In ocean engineering and coastal environmental studies, local scour around a submerged structure is a typical issue, which is affected by the inclination of the structure. To investigate the effect of inclination directions and angles on flow structure and the bed morphology, a three-dimensional numerical model of a submerged inclined cylinder was...

Tidal flow structures and tidal energy in Zhoushan Archipelago sea area are impacted by the land reclamation nearby. The spatial and temporal changes of the tidal flow structure and tidal energy distribution due to land reclamation in Zhoushan Islands were examined using the FVCOM ( finite volume coastal ocean model). The results show that from 198...