• Reynolds Number Transition Zone

. As with many fluid mechanics problems, the first order of business is to determine the Reynolds number of the flow. If you don't have a velocity by which to calculate the Reynolds Number, you will need to assume either a velocity, or a initial friction factor. If you assume an initial velocity, proceed as usual. If you assume a friction factor (I like 0.02), jump to step 10. If done correctly, you will converge at the same answer. Refer to the Moody Chart.

If the Reynolds Number falls in the Laminar or Transition range, refer to appropriate equations. If however the flow is in the Turbulent range, we are ready to proceed with the Moody Chart. Compute the relative pipe roughness.

This value is the roughness of the pipe, divided by the diameter of the pipe. REMEMBER, you want this to be unitless, so ensure that the roughness and diameter are in matching units. ALSO REMEMBER, just because the wall roughness may be zero, making the relative roughness zero, this does NOT mean that the friction factor will be zero. Find the line referring to your relative roughness on the right side of the diagram. In the case that your value does not have a printed line, imagine a line paralleling the nearest line representing your relative roughness. It may be helpful to sketch in this line.

Follow this line to the left as it curves up until to reach the vertical line corresponding to your flow's Reynolds Number. Mark this point on the Chart. Using a straight edge, follow the point straight left, parallel to the x axis, until you reach the far left side of the chart. Read off the corresponding friction factor. Calculate the energy losses knowing the friction factor.

Calculate a new velocity and Reynolds Number. Compare your new Reynolds Number with your previous value. If the Reynolds number is appreciably different from your previous value, repeat the calculations with this new Reynolds Value. If however it is close to your previous value, your answer has converged, and you are finished. Let's imagine we calculate a Reynolds Number of 4x10^4 (yes I'm rigging for simplicity).

We see that this is in the Reynolds Number range for turbulent flow, so we proceed with the Moody Chart. Next, let's say we calculate a unitless relative roughness of 0.003. From here we sketch a line following the curve contours, going left, as see in the red line below.

We follow this line until you Reynolds number value from before, and mark this point. From here, we look straight left, shown by the orange line, until we hit the left margin of the chart. Here we read off our value of 0.03.At this point, we would compute a new velocity, and a new Reynolds Number, and iterate if necessary. Both the Reynolds number and relative roughness are unitless values when computed correctly, therefore the Moody Chart is unitless, so the same chart applies to US Customary and SI unit systems.

Another common mistake when reading the Moody Diagram is improper interpolation between lines and points. Be aware of the logarithmic nature of the axes and labels values, halfway between the values is NOT halfway between the points. This system will only work for steady state analysis. If the problem is transient, you can still solve for the end state, however no information can be gleaned from what happens between initial state and steady state.

To do this, other methods including numerical analysis, or FEA will be necessary. For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: Show Details NecessaryHubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.LoginThis is necessary to sign in to the HubPages Service.Google RecaptchaThis is used to prevent bots and spam.

AkismetThis is used to detect comment spam. HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site.

Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.Amazon Web ServicesThis is a cloud services platform that we used to host our service. CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. FeaturesGoogle Custom SearchThis is feature allows you to search the site. Google MapsSome articles have Google Maps embedded in them. Google ChartsThis is used to display charts and graphs on articles and the author center.

Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature.

Google YouTubeSome articles have YouTube videos embedded in them. VimeoSome articles have Vimeo videos embedded in them. PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature.

MavenThis supports the Maven widget and search functionality. MarketingGoogle AdSenseThis is an ad network. Google DoubleClickGoogle provides ad serving technology and runs an ad network. Index ExchangeThis is an ad network.

SovrnThis is an ad network. Facebook AdsThis is an ad network. Amazon Unified Ad MarketplaceThis is an ad network.

AppNexusThis is an ad network. OpenxThis is an ad network. Rubicon ProjectThis is an ad network.

TripleLiftThis is an ad network. Say MediaWe partner with Say Media to deliver ad campaigns on our sites.

The critical Reynolds number is associated with the laminar-turbulent transition, in which a laminar flow becomes turbulent. This is an extraordinarily complicated process, which at present is not fully understood.

Critical Reynolds Number for Flow in a PipeFor flow in a pipe of diameter D, experimental observations show that for “fully developed” flow, the critical Reynolds number is about Re d,crit = 2300. Laminar flow. For practical purposes, if the Reynolds number is less than 2000, the flow is laminar. The accepted transition Reynolds number for flow in a circular pipe is Re d,crit = 2300. Transitional flow. At Reynolds numbers between about 2000 and 4000 the flow is unstable as a result of the onset of turbulence.

These flows are sometimes referred to as transitional flows. Turbulent flow. If the Reynolds number is greater than 3500, the flow is turbulent.Note that, the critical Reynolds number is different for every geometry. Heat Transfer:. Fundamentals of Heat and Mass Transfer, 7th Edition. Bergman, Adrienne S. Lavine, Frank P. John Wiley & Sons, Incorporated, 2011.

ISBN: 253. Heat and Mass Transfer. McGraw-Hill Education, 2011. ISBN: 866.

Fundamentals of Heat and Mass Transfer. C. Kothandaraman. New Age International, 2006, ISBN: 722. U.S. Department of Energy, Thermodynamics, Heat Transfer and Fluid Flow. DOE Fundamentals Handbook, Volume 2 of 3. May 2016.Nuclear and Reactor Physics:. J.

Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983). G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988. U.S.

Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993. Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 9414.Advanced Reactor Physics:. K. Neuhold, Introductory Nuclear Reactor Dynamics, American Nuclear Society, 1985, ISBN: 0-894-48029-4. D.

Reynolds Number Transition Zone

Hetrick, Dynamics of Nuclear Reactors, American Nuclear Society, 1993, ISBN: 0-894-48453-2.