Terms and Conditions — Streakline

Streakline is published on Google Play as "Streakline: Pocket CFD".

Last updated: 20 - 08 -2026

1. Agreement

These Terms govern your use of the Streakline mobile application ("the App"), published by Farrel Kent, an individual developer based in Jakarta, Indonesia ("we", "us").

By installing or using the App you agree to these Terms. If you do not agree, do not use it. Our handling of personal data is described separately in our Privacy Policy at https://farrelkk.github.io/pocketcfd-legal/privacy.html, which forms part of these Terms.

2. What Streakline is — and what it is not

Streakline is an educational and exploratory fluid dynamics tool. It solves a two-dimensional lattice Boltzmann model on a coarse grid sized to run in real time on a phone.

It is not engineering software, and its output must not be relied upon for engineering, design, certification, safety or commercial decisions.

This is not boilerplate caution. Specific and inherent limitations include:

• the simulation is two-dimensional; real flows are not
• the scheme is weakly compressible and isothermal, with no turbulence model; compressibility error grows with the Mach number, which the App displays once it becomes significant
• the domain is narrow, so blockage effects inflate drag relative to open-air conditions
• resolution is low by professional standards and boundary layers are under-resolved
• the top and bottom boundaries are a numerical construct, not a physical wall or open air
• achievable Reynolds numbers are far below most real applications
• the solver applies a small artificial perturbation behind the body during start-up to trip the wake into shedding; results reflect that nudge as well as the geometry
• viscosity is floored for numerical stability, so at high inlet speeds the Reynolds number actually solved is lower than the one requested (the App marks this with a ⚠)

Coefficients reported by the App are indicative of trends and comparisons within the App. They are not validated against experiment, are not a substitute for a qualified CFD study, wind-tunnel testing or professional judgement, and must not be presented as engineering results.

You are solely responsible for any decision you make on the basis of output from the App.

3. Licence

We grant you a personal, non-exclusive, non-transferable, revocable licence to install and use the App on devices you own or control, for your own purposes, in accordance with these Terms and the rules of the app store you obtained it from.

You may use simulation results, images, videos and CSV data you generate with the App for any lawful purpose, including commercially, subject to section 2.

4. Free tier and Streakline Pro

The free tier includes three hand-drawn geometries per calendar day, resetting at local midnight, together with the standard shape library at draft resolution.

Streakline Pro is a one-time purchase. It removes the daily limit and unlocks image import, higher-resolution grids, the extended shape library, saved shapes, data export, recording and watermark-free capture.

We may change what is included in each tier for future purchases. We will not remove a feature you have already paid for from your copy of the version you bought it in.

5. Payment, ownership and restoring

• Payment is taken by Google Play, not by us. We never receive or handle your payment details. Google is the seller of record.
• The price shown in the App is the live price from the store for your country, including any taxes the store collects. A price shown before the store responds is a list price and may differ in your country; the store's price is the one you pay.
• Nothing renews. There is no subscription, no recurring charge and nothing to cancel.
• Your purchase is tied to the Google account that made it, not to a device or an app version. Updating the App does not affect it.
• Restoring: if you reinstall, clear the app's data or move to a new device, use Restore purchases in the Pro tab. Restoring is free and unlimited on any device signed in to the same store account. A purchase made on a different account cannot be restored to yours.

6. Refunds

Refunds are handled by Google Play under Google's refund policies, not by us. Request one through your Google Play account; we can raise a request on your behalf but cannot grant one directly. Have your order ID (GPA.…) from your receipt email ready.

Nothing here limits refund or cancellation rights you have under mandatory consumer protection law — including Indonesian Law No. 8 of 1999 on Consumer Protection and, in the EEA or UK, statutory withdrawal and conformity rights.

7. Future versions

Your purchase unlocks Pro in the version of the App you bought it in and in updates we release to that version. If we publish a substantially new product in future — a separate listing rather than an update — it may be a separate purchase. We will say so clearly before you buy it.

8. Promotional and unlock codes

We may issue promotional codes granting access to Pro features. Codes are personal, have no cash value, are not transferable and may be withdrawn or invalidated at any time. Sharing, publishing, reselling or circumventing a code is a breach of these Terms.

9. Your content

Shapes you draw, images you import and results you produce remain yours. We claim no ownership over them and, as described in the Privacy Policy, we never receive them.

You are responsible for having the right to use any image you import. Do not import content that infringes someone else's copyright or other rights.

10. Acceptable use

You agree not to:

• reverse engineer, decompile or disassemble the App, except where applicable law expressly permits it despite this restriction
• circumvent, disable or tamper with the free-tier limits, ownership checks or any other technical measure governing access to paid features
• redistribute, resell, sublicense, rent or make the App available to third parties as a service
• use the App unlawfully, or in a way that damages, disables or overburdens it
• present output from the App as validated or professionally certified engineering analysis

11. Intellectual property

The App — including its source code, solver implementation, shape library, interface design, name and icon — is owned by us and protected by copyright and other intellectual property laws. Nothing in these Terms transfers any of those rights to you. The underlying physics and numerical methods are public knowledge and are not claimed by us.

12. Availability and changes

We may update, change or discontinue the App or any feature at any time, and may stop distributing it entirely. The App runs locally and does not require our servers, so we make no uptime commitment — there is no service to keep up. If we discontinue the App, copies already installed continue to work; we cannot guarantee the store will keep them available for re-download.

13. Disclaimer of warranties

To the fullest extent permitted by law the App is provided "as is" and "as available", without warranty of any kind, express or implied, including implied warranties of merchantability, fitness for a particular purpose, accuracy and non-infringement.

We do not warrant that the App will be error-free, that results will be accurate or physically correct, or that it will run on any particular device.

14. Limitation of liability

To the fullest extent permitted by law:

• we are not liable for any indirect, incidental, special, consequential or punitive damages, or for loss of profit, revenue, data, goodwill or business opportunity, arising from your use of or inability to use the App
• we are specifically not liable for any loss, cost, injury or damage arising from reliance on simulation output, in line with section 2
• our total aggregate liability arising out of or relating to the App is limited to the greater of (a) the amount you actually paid us for the App, or (b) IDR 500,000

Nothing in these Terms excludes or limits liability that cannot lawfully be excluded, including for death or personal injury caused by negligence, for fraud, or under mandatory consumer protection law.

15. Indemnity

You agree to indemnify us against claims, losses and reasonable costs arising from your breach of these Terms, your misuse of the App, or your use of content you had no right to import.

16. Termination

You may stop using the App at any time by uninstalling it. We may suspend or terminate your licence if you materially breach these Terms — in particular sections 8 and 10. Sections 2, 9, 11, 13, 14, 15 and 18 survive termination. Termination does not automatically refund a purchase; see section 6.

17. App stores

You obtained the App from Google Play (and, if we publish there, the Apple App Store). Your use is also subject to that store's terms.

This agreement is between you and us, not with Google or Apple. Those companies are not responsible for the App or its content and have no obligation to provide support or maintenance for it. Where the App is distributed through the Apple App Store, Apple and its subsidiaries are third-party beneficiaries of these Terms and may enforce them against you.

18. Governing law and disputes

These Terms are governed by the laws of the Republic of Indonesia, without regard to conflict of law rules. Any dispute we cannot resolve informally will be submitted to the competent District Court (Pengadilan Negeri) of Jakarta, Indonesia.

If you are a consumer resident in the EEA or UK, this does not deprive you of the protection of mandatory consumer law in your country of residence, or of the right to bring proceedings in your local courts.

Please email us first. Most problems are a bug, and we would rather fix it.

19. Contact

Farrel Kent Kuntadihardja Jakarta, Indonesia farrelekntk@gmail.com

These Terms apply to Streakline version 1.0.0