# RYURAKU - Fluid Dynamics — Learn physics with fluid sims

> Learn physics with fluid sims (iPhone/iPad app by Fuji Bit Inc..)

- Source: https://appshunter.io/ios/app/ryuraku-fluid-dynamics/id6760613893 (this page in markdown: same URL + `.md`)
- Developer: [Fuji Bit Inc.](https://appshunter.io/developer/1874205957)
- Category: Education, Utilities
- Price: Free
- Age rating: 4+
- Requires: iOS 15.0 · 26 MB
- Languages: American English, French (France), German (Germany), Hindi, Indonesian, Italian, Japanese, Korean, Brazilian Portuguese, Russian and 6 more
- Released: 2026-03-18
- Data updated: 2026-10-25

## What is RYURAKU?

RYURAKU is an interactive educational simulation app for experiencing fluid dynamics phenomena firsthand.

Developer: Fuji Bit Inc.

The 6th title in the SUUGAKU / BUTURAKU / DENRAKU / HARAKU / NETURAKU series. The theme is "flow." Discover the wonders of fluid physics through 12 hands-on simulations.

12 simulations in 3 categories:

- Flow basics
- Streamlines: particles reveal potential flow around a cylinder in a uniform stream. Drag the obstacle and watch the flow field change in real time.
- Bernoulli's Principle: flow through a Venturi tube with live pressure gauges. Watch speed rise and pressure drop where the pipe narrows, and see A1v1 = A2v2 at work.
- Reynolds Number: laminar-turbulent transition in pipe flow. Adjust speed, viscosity and diameter and see the dramatic change at Re ≈ 2300.
- Boundary Layer: a boundary layer growing over a flat plate, from the laminar Blasius solution to turbulent transition at Re_x ≈ 5×10^5.
- Darcy's Law: slow flow through porous media such as sand or rock. Adjust permeability, pressure gradient and porosity to experience q = (k/μ)·∇P, the law behind groundwater, oil reservoirs and filters.

- Vortices & lift
- Vortex: point vortices and their mutual induction. Tap to add a counterclockwise vortex, long-press for clockwise.
- Kármán Vortex Street: alternating vortex shedding behind a cylinder, with live Strouhal and Reynolds numbers.
- Lift Force: flow around an airfoil and how lift and drag arise. Change the angle of attack or camber and watch the force vectors.
- Magnus Effect: asymmetric flow and a sideways force on a spinning cylinder: the physics of curveballs and banana kicks.

- Water & gravity
- Buoyancy (new): Archimedes' principle. Change the object and fluid densities to find where things float, sink or hang in balance. Drag the object under, let go, and watch it bob until it settles with a submerged fraction of ρ_s/ρ_f.
- Torricelli's Law (new): water jetting from a hole in a tank. See the exit speed v = √(2gh), the falling water level and the jet range R = 2√(y₀h). Drag the hole to find the height that throws the water farthest.
- Surface Wave: free-surface gravity waves. As the depth-to-wavelength ratio changes, particle orbits shift smoothly from circles (deep water) to flattened ellipses (shallow water).

Features:
- Real-time parameter adjustment for every simulation
- A hint on how to try each screen, plus an explanation with formulas
- Live physics formulas and values
- Works with large text sizes, landscape, iPad and Split View
- Taps and drags can also be done with buttons and sliders (works with VoiceOver and Switch Control)
- 16 languages (English, Japanese, Chinese Simplified / Traditional, Korean, Spanish, Portuguese, German, French, Hindi, Indonesian, Russian, Italian, Turkish, Thai, Vietnamese)
- Dark mode / Light mode

Pricing & ads:
- Free. No in-app purchases, subscriptions or paid unlocks
- A banner ad (Pangle) is shown at the bottom of the screen
- Ads are personalized only if you allow tracking (ATT). You can also turn off personalized ads from "About this app" > "Ad settings"

Recommended for:
- Students studying fluid dynamics in physics class
- Anyone who wants to understand how flow behaves
- Teachers looking for interactive teaching materials
- Anyone interested in aeronautics or fluid mechanics

## Is RYURAKU safe?

Not enough ratings yet to assess RYURAKU.

## Is RYURAKU legit?

RYURAKU - Fluid Dynamics appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for RYURAKU is 65 out of 100 points across 7 verification signals from App Store and developer data.


## Version history (last 5 releases)

### 5.0 — 2026-10-18

- New Buoyancy simulation (Archimedes' principle: float, sink or balance)
- New Torricelli's Law simulation (how fast and how far water jets from a tank)
- Now 12 simulations, grouped on the home screen into Flow basics, Vortices & lift, and Water & gravity
- Redesigned screens: a hint on every screen, improved control panel, better support for large text, landscape and iPad
- Taps and drags can now also be done with buttons and sliders, for VoiceOver users
- Fixed simulations shifting out of place after rotating the screen or using Split View
- Now available in 16 languages
- Ads now served by Pangle, with a new "Ad settings" option

### 4.0 — 2026-05-11

- 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

### 3.0 — 2026-04-01

• Added Boundary Layer simulation (laminar-to-turbulent transition over flat plate, Blasius solution, velocity profiles)
• Added Magnus Effect simulation (spinning cylinder lift force, stagnation point shift, circulation visualization)
• Now 8 simulations in total

### 2.0 — 2026-03-25

• Added Kármán Vortex Street simulation (alternating vortex shedding behind a cylinder, Strouhal number display)
• English language support (auto-detects device language)
• All UI text fully localized

### 1.0 — 2026-03-18

No release notes.

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## More apps by Fuji Bit Inc.

- [RENGOKU: Time Attack Pachinko](https://appshunter.io/ios/app/rengoku-time-attack-pachinko/id6758652751)
- [SUUGAKU](https://appshunter.io/ios/app/suugaku/id6759102221)
- [BUTURAKU](https://appshunter.io/ios/app/buturaku/id6759213255)
- [DENRAKU - Electromagnetism Sim](https://appshunter.io/ios/app/denraku-electromagnetism-sim/id6759393816)
- [PAKEDOU](https://appshunter.io/ios/app/pakedou/id6759820254)
- [OKURERUNA！](https://appshunter.io/ios/app/okureruna/id6759956971)

All apps by Fuji Bit Inc.: https://appshunter.io/developer/1874205957

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-10-25.*