Related Experiment Video
Updated: Jul 15, 2026
10:35
A Protocol for Conducting Rainfall Simulation to Study Soil Runoff
Published on: April 3, 2014
Geometry controls momentum flux in the sprinkler problem
Jesse Etan Smith1,2, Mingxuan Zuo1, Will Kuhlke2
1Applied Math Lab, Courant Institute School, Department of Mathematics, New York University, New York, NY 10012.
Summary
Experiments reveal the reverse sprinkler effect relies on fluid momentum fluxing into the device, not just angular momentum. This finding clarifies the physics of hydro-mechanical devices and flow-structure interactions.
Area of Science:
- Fluid mechanics
- Hydro- and aero-mechanical systems
- Flow-structure interactions
Background:
- The reverse sprinkler problem, a classic fluid dynamics enigma, lacks experimental clarification despite numerous proposed theories.
- Understanding these systems is crucial for advancing hydro- and aero-mechanical device principles.
Purpose of the Study:
- To experimentally investigate the physics behind aspirating fluid flows through curving tubular arms.
- To differentiate between competing hypotheses for the reverse sprinkler effect.
- To elucidate the fundamental principles governing flow-structure interactions in such devices.
Main Methods:
- Designed and conducted experiments with tailored device geometries.
- Measured device motions, torques, and internal/external fluid flows.
- Analyzed fluid momentum flux and its correlation with observed rotation.
Main Results:
- Observations contradict theories based solely on total fluid angular momentum or outer flow distributions.
- A strong correlation was found between torque direction and the momentum flux of fluid entering the device.
- The geometry of the arms dictates the mass-to-momentum flux conversion.
Conclusions:
- The reverse sprinkler operates via isotropic fluid input and swirl-up, generating angular momentum within the arms.
- A portion of this generated angular momentum drives the device's rotation.
- This research provides fundamental insights into flow-structure interactions and energy harvesting applications.
Related Concept Videos
01:14Conservation of Mass in Moving, Nondeforming Control Volume
Stormwater detention basins are essential in managing runoff during heavy rainfall, particularly in urban areas where impervious surfaces increase the risk of flooding. Understanding the conservation of mass in these systems allows engineers to optimize basin performance, balancing inflow, outflow, and water storage.
In the context of a detention basin, the conservation of mass states that the total mass of water entering the basin must equal the mass leaving the basin plus any accumulation of...
In the context of a detention basin, the conservation of mass states that the total mass of water entering the basin must equal the mass leaving the basin plus any accumulation of...
01:15Application of the Linear Momentum Equation
The application of the linear momentum equation can be used to analyze the forces needed to hold a 180-degree pipe bend in place with flowing water. In this case, water flows through the bend with a constant cross-sectional area of 0.01 square meters and a flow velocity of 15 meters per second. The pressure at the entrance is 0.2 Megapascals and the pressure at the exit is 0.16 Megapascals.
The goal is to determine the force components in the x and y directions to hold the pipe in place. Since...
The goal is to determine the force components in the x and y directions to hold the pipe in place. Since...
01:13Linear Momentum in Control Volume
Newton's second law is applied to obtain the linear momentum in a control volume in a fluid system. According to this law, the rate of change of linear momentum is equal to the sum of external forces acting on the system. When a control volume matches the fluid system at a specific moment, the forces acting on both are identical. Reynolds transport theorem helps explain this by breaking down the system's linear momentum into two components: the rate of change of linear momentum within the...
01:28Pipe Flowrate Measurement: Problem Solving
A spray tank system is engineered to uniformly distribute a pest-control liquid across plants by using a pressurized mechanism. The tank, pressurized to 150 kPa, holds the pesticide at a height of 0.80 meters. Liquid flows from the tank through a 1.9 meter pipe with a diameter of 0.015 meters, angled at 0.698 radians, ultimately reaching a 0.007 meter nozzle that sprays the pesticide. Accurate calculation of the system's flow rate is crucial to ensure uniform application, and this is achieved...
01:18Newtonian Fluid: Problem Solving
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
01:15Integration Applied to Polar Coordinates to Find Areas
A rotating lawn sprinkler with an uneven spray pattern produces a variable reach as it distributes water in different directions. This directional variation in spray distance can be effectively described using polar coordinates, where the distance from the center is represented as a function of the angle of rotation. The path traced by the spray then forms a polar curve, which captures the irregularities in the sprinkler’s reach across the full rotation.To calculate the total area watered by...