A student from our laboratory will present research on Tonle Sap Lake in Cambodia at an international conference to be held in Phnom Penh, the capital of Cambodia.

The research aims to simulate water flow within the lake and investigate how bacteria are transported by these currents. In large lakes, wind-driven currents play an important role in water circulation. Therefore, we are also examining how including wind data in the simulation affects the results.

Simulation of Bacterial Transport Throughout Tonle Sap Lake

(Left: Without considering wind effects; Right: With wind effects included)

 

Simulation of Bacterial Transport in the Northern Part of Tonle Sap Lake

(Left: Without considering wind effects; Right: With wind effects included)

 

We will present our research using DRUM, our coupled human–fluid simulation model, at a conference next month.

In flowing water, strong hydrodynamic forces act on the human body, making it easy for a person to be carried downstream by the current. Even small bumps and irregularities on the riverbed offer little resistance to this movement.

Our research aims to quantify how rapidly a human body is transported under different flow velocities. By understanding this relationship, we hope to help estimate the approximate search areas for victims of water-related accidents.

Dr. Davin from the Institute of Technology of Cambodia visited our laboratory as a visiting researcher.

We are conducting collaborative research to apply our three-dimensional flow simulation model to the transport of pathogenic bacteria in Tonle Sap Lake, Cambodia.

During the visit, Dr. Davin learned how to configure and run the simulation model.

The photograph was taken during a laboratory seminar, where Dr. Davin gave a presentation about their research and Cambodian culture.

A hydraulic jump causes the flow to change rapidly and generates strong vortices. The visualization below shows an analysis of the motion of a human-body model within a hydraulic jump.

Following our previous post, we would like to share another visualization result from the DRUM model. When high-velocity flow enters a deeper water region, a discontinuous change in water level known as a hydraulic jump occurs. Vortices are generated within the hydraulic jump, and we are investigating what happens when a person becomes caught in this flow.

Here is another visualization result. As graduation approaches, various research results are beginning to emerge, and this is one example.

The simulation shows a case in which a person’s foot becomes trapped in flowing water. The flow velocity is 2 m/s, which is roughly comparable to that of a river during heavy rain. Although a buoyancy force of 4 kgf is applied to the torso, the force of the current presses the body down so strongly that the upper body cannot be raised.

To gain a physical understanding of phenomena from simulation results, visualization is essential. In particular, it is important to determine what kinds of graphs and images should be created to effectively interpret the results.

We encourage our students to use their own creativity and ideas to produce clear and meaningful visualizations.

The example below shows preliminary results from an ongoing study investigating whether life jackets could help prevent accidents during surfing.

Field Observations along the Senegal River – Senegal and Mauritania, West Africa

During the rainy season, extensive flooding occurs in the lower Senegal River basin in West Africa, causing significant difficulties for rice cultivation. Our research aims to simulate the extent of flooding and assess the resulting damage, as well as the potential effectiveness of future flood control measures.

Field investigations are essential for developing reliable numerical simulations. On this research trip, we entered Senegal and then traveled overland to Mauritania, conducting field observations of the Senegal River, which forms the border between the two countries.

We arrived in Senegal through Dakar, a city famous for the Paris–Dakar Rally. Our first visit was to the Organisation pour la Mise en Valeur du fleuve Sénégal (OMVS), the Senegal River Basin Development Organization, whose member countries include Senegal, Mauritania, and Mali. We introduced our research activities and gathered information from local staff.

Rainfall appeared to be particularly abundant during this rainy season, and Senegal was covered in lush greenery.

Even in the urban areas of Dakar, many baobab trees can be seen.

To prepare for our field observations, we traveled from Dakar, the capital of Senegal, to Saint-Louis in the north. These photographs were taken from our vehicle during the journey.

 

Saint-Louis is a UNESCO World Heritage Site known for its historic colonial architecture dating back to the period of French rule.

Saint-Louis is located near the mouth of the Senegal River. Using the city as our base, we traveled upstream and measured flow velocities at several locations while crossing the river by boat. On this trip, we traveled approximately 200 km by car to reach the town of Podor.

We then crossed the Senegal River northward into Mauritania and continued our field observations from the Mauritanian side. We used Rosso, the third-largest city in Mauritania, as our base.

Flooding was spreading across the areas surrounding the Senegal River during the rainy season.

 

The irrigation canals appeared to be simple excavated channels, and there were no obvious levees along the banks of the Senegal River.

We measured flow velocities from a bridge over one of the major tributaries flowing through the Mauritanian side of the river basin.

After completing our field observations, we traveled to Nouakchott, the capital of Mauritania. Our journey took us northward along the western edge of the Sahara Desert. We enjoyed views of the desert from the vehicle while traveling along a national highway filled with potholes.

Nouakchott is a modern city. Here, we visited local markets as a preliminary step toward conducting a survey of consumer preferences.

At the fish market on the Atlantic coast, fishermen set out to sea directly from the sandy beach.

This is a market in the city center, bustling with activity and full of energy.

 

 

We are participating in an international collaborative research project on water flow in Tonle Sap Lake, Cambodia.

A student from our laboratory presented their research at a workshop held at the Shiko Memorial Museum in Kanazawa, Japan.

We also had the opportunity to exchange ideas and information with professors and students specializing in satellite remote sensing. It was a very exciting and stimulating experience!

We have added new simulation examples using our drowning simulation model, DRUM. Please visit the DRUM model introduction page for more details.