Articles with tag: "IceVal"

1. Testing Messinger Freezing Fraction Correlations with the IceVal Database

   "an empirical relationship was obtained which correlated ice accretion thickness and ice angles with theoretical impingement parameters." ¹

   

   Introduction

   Studies have correlated icing conditions to ice shapes and their effects. Here, we will test one using the 3332 experimental ice shapes cases in the IceVal database ¹ without ice protection.

   The studies had well-planned series of test conditions for their objectives. However, when we use all 3332 IceVal experimental shapes from tests with diverse objectives, things can get messy.

   We will see that the final results are surprisingly good.

   NASA/CR-2005-213852 ³

   NASA/CR-2005-213852 "Evaluation and Validation of the Messinger Freezing Fraction" has been reviewed previously in Conclusions of the Ice Shapes and Their Effects thread.

   It looked at correlating ice shape parameters to calculated leading edge freezing fraction.

   The test cases within it are now a subset of the IceVal database.

   40 condition were tested to verify an implementation …

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2. Swept Airfoil Cases in IceVal

   "Use of these relationships allows the direct determination of ice shapes adjusted for any given icing and flight condition as well as for size and sweep of the airfoil" ¹

   
   

   Experimental ice shapes compared to a LEWICE analysis.

   Summary

   There are 41 swept airfoil cases in the IceVal database ².

   The quote at the top from Wilder briefly describes the the empirically based analytical method he described in ¹. However, it is not directly applicable to airfoils other than the ones he considered, which had dozens of icing tunnel ice shapes tests each. For more details on Wilder's method, see Wilder.

   LEWICE ³, and other codes, offer potentially more widely applicable methods of ice shape prediction in swept airfoils.

   LEWICE analysis for these cases tends to produce ice shapes that are consistently too small compared to experiment.

   Empirically derived adjustments to the inputs to LEWICE are discussed that improve the …

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3. Running LEWICE version 3.2.3 for the IceVal cases

   "The resulting analysis showed that LEWICE compared well to the available experimental data." ¹

   
   

   An example of a good comparison between analysis and experiment.

   Introduction

   The IceVal database ², and its predecessors, were originally assembled to validate the LEWICE ³ ice shape prediction code.

   Here, we will repeat that analysis with a more recent version of LEWICE, and look at the effects of using "corrected" angle of attack values in the analysis.

   The LEWICE ice shapes results in the IceVal database were apparently run with LEWICE version 3.2.2 (We will abbreviate that as the Database LEWICE shape). The IceVal users guide is not explicit, other than "the latest version of the LEWICE ice shape prediction code". The 2008 LEWICE validation report was written at about the same time. It does not mention IceVal, but the validation report was for LEWICE version 3.2.2.

   Comparisons with all IceVal …

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4. A Geometric Analysis Method

   "This demonstrates that the automated process cannot (yet) be substituted for good engineering judgment."

   From the LEWICE manual. ¹

   
   

   A case where two methods detected similar upper surface ice horns.

   Introduction

   Reviewing 6000+ ice shape assessments to verify that they agree with engineering judgement is a daunting task. Even with professionalism and due-diligence, debatable results may be missed. So, there is motivation to automate the process as much as possible.

   Here, I describe a step toward that goal. It is a work in progress, not a completed product.

   Using the IceVal database to validate an assessment method

   The IceVal database will be used here to validate a different comparison assessment method. This is one of the uses envisioned when compiling the database ²:

   ... by compiling a comprehensive database consisting of a standardized, reliable data set, and combining that with an easy-to-use graphical user interface (GUI), providing quick and easy access …

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5. Overall comparison assessments between experiment and LEWICE

   "It is possible for any (or all!) ... parameters to be incorrectly output."

   
   

   A case with identified horn locations that are debatable.

   Introduction

   Assessments of LEWICE ice shapes compared to experiment have been published twice.

   The LEWICE THICK utility program was uses to identify ice horn locations and maximum heights. However, engineering judgement was used to adjust some values in the IceVal database. Cases with questionable ice horn identifications can be found in the database.

   The difficulty of consistently identifying ice horns affects the comparison assessment between LEWICE and experiment.

   Published assessments

   The overall comparison of LEWICE ¹ analysis to experimental data to has been published twice.

   The first was in 1999 ², and included 800 experiment cases. The second was in 2008 ³, and had more than 3000 experimental cases. These are the data that are included in the IceVal database ⁴.

   The 1999 Assessment

   The assessment published in 1999 …

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6. A Tour of the IceVal DatAssistant

   "... all publicly available IRT-generated experimental ice shapes with complete and verifiable conditions have now been compiled into one electronically-searchable database"

   NASA Report E-16236 ¹.

   
   Public Domain image from NASA Report Number: E-16236.

   A quick tour of the IceVal DatAssistant

   The IceVal DatAssistant is available from NASA. It runs on the Windows operating system (only).

   The IceVal DatAssistant can do several functions. The main interest here is the database of experimental run conditions and results.

   The tables of primary interest are IceShapeData, RunSpecs, and SprayConditions.

   
   Public Domain image from NASA Report Number: E-16236.

   In the time span 1988 to 2008 that the database covers, experimental test results were measured by cutting a thin slot into the ice, inserting a pre-made cardboard template, and manually tracing the ice shape. These were later digitized, and included in the database.

   
   Public Domain image from NASA Report Number: E-16236.

   Range of conditions tested

   The primary …

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7. 6000 Ice Shapes - the IceVal DatAssistant

   "As with any scientific endeavor, the foundation of icing research ... is the data acquired during experimental testing."

   NASA Report E-16236 ¹.
   
   

   
   

   4132 ice shapes for the NACA0012 airfoil.

   [Yes, that is how it is spelled.]

   The IceVal DatAssistant ¹, ² from NASA contains 6330 ice shapes from experiments in the NASA Icing Research Tunnel ³ (3665 shape tracings) and from analysis with LEWICE ⁴ (2965 ice shapes).

   Significant uses of the data were the LEWICE validation reports published in 1998 ^{5 6} and 2008 ⁷, which established measures for the comparison of LEWICE analysis results to experimental data.

   These data are tremendous aids to researchers and developers of icing analysis codes and test methods. It has been 27 and 18 years since these were published (respectively), and we should celebrate that the utility of the data has held up well. However, given that an entire generation of workers in the …

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