RYURAKU
Learn physics with fluid sims
Free · Designed for iPad. Not verified for macOS.
Explore 10 fluid simulations: streamlines, Bernoulli, vortices, Reynolds, lift, Kármán, boundary layers, Magnus, Darcy flow, and surface waves — all in real time.
RYURAKU is an interactive educational simulation app for experiencing fluid dynamics phenomena firsthand.
The 6th installment in the SUUGAKU / BUTURAKU / DENRAKU / HARAKU / NETURAKU series. The theme is "flow." Discover the wonders of fluid physics and the depth of physical laws through 10 hands-on simulations.
[10 Simulations]
1. Streamline Visualization
Visualize potential flow around a cylindrical obstacle in a uniform stream using particles. Drag the obstacle to move it and observe how the flow field changes in real time.
2. Bernoulli's Principle
Visualize flow inside a Venturi tube. Watch how flow speed increases and pressure drops as the pipe narrows, with real-time pressure gauges. Intuitively understand the continuity equation A1v1 = A2v2.
3. Vortex
Simulate point vortex creation and mutual induction. Tap to add a counterclockwise vortex, long press for clockwise. Observe complex vortex motion patterns.
4. Reynolds Number
Visualize laminar-turbulent transition in pipe flow. Adjust flow speed, viscosity, and pipe diameter to manipulate the Reynolds number and experience the dramatic change at Re ≈ 2300.
5. Lift Force
Visualize flow around an airfoil and the mechanisms behind lift and drag generation. Change the angle of attack or camber to see how the lift coefficient varies, with force vectors displayed in real time.
6. Kármán Vortex Street
Visualize alternating vortex shedding behind a cylinder. Strouhal and Reynolds numbers are displayed in real time, helping you understand the relationship between shedding frequency, flow speed, and cylinder diameter.
7. Boundary Layer
Visualize boundary layer development over a flat plate. Observe how viscous effects slow the fluid near the wall. Experience the transition from laminar (Blasius solution) to turbulent flow at the critical Reynolds number Re_x ≈ 5×10^5.
8. Magnus Effect
Visualize the asymmetric flow and lift force around a spinning cylinder. Understand the physics behind curveballs in baseball, banana kicks in soccer, and slice shots in golf.
9. Darcy's Law [NEW]
Visualize slow flow through a porous medium such as sand or rock. Adjust permeability, pressure gradient, and porosity to experience the law q = (k/μ)·∇P that governs groundwater, oil reservoirs, filters, and soil seepage.
10. Surface Wave [NEW]
Visualize free-surface gravity waves. As the depth-to-wavelength ratio changes, particle orbits transition smoothly from circles (deep water) to flattened ellipses (shallow water). Directly observe the Airy dispersion relation ω^2 = gk·tanh(kh).
[Features]
- Real-time parameter adjustment for all simulations
- Live physics formulas and numerical values
- Japanese / English support
- Dark mode / Light mode
- Clean, intuitive UI
[Monetization & Ads]
- This app is free to download and use
- No in-app purchases, no subscriptions, no paid unlocks
- A banner ad (Google AdMob) is shown at the bottom of the screen
- On iOS, personalized ads are only delivered after the user grants App Tracking Transparency (ATT) permission
[Recommended for]
- Students studying fluid dynamics in physics class
- Anyone who wants to intuitively understand the behavior of flow
- Teachers looking for interactive teaching materials
- Anyone interested in aeronautical engineering or fluid mechanics
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
- Added Darcy's Law simulation (porous-medium flow with permeability and pressure gradient)
- Added Surface Wave simulation (Airy linear theory, continuous shallow-to-deep water transition)
- Now 10 simulations in total
- Added About dialog and app information display
The developer, Fuji Bit Inc., indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Used to Track You
The following data may be used to track you across apps and websites owned by other companies:
- Identifiers
- Usage Data
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Identifiers
- Usage Data
- Diagnostics
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Fuji Bit Inc.
- Size
- 25.2 MB
- Category
- Education
- Compatibility
Requires iOS 13.0 or later.
- iPhone
Requires iOS 13.0 or later. - iPad
Requires iPadOS 13.0 or later. - iPod touch
Requires iOS 13.0 or later. - Mac
Requires macOS 11.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- Japanese
- Age Rating
4+
- 4+
- Contains
Advertising
- Copyright
- © 2026 Fuji Bit