Effects of freestream nonequilibrium on convective heat transfer to a blunt body

Gökçen, Tahir

doi:10.2514/3.780

Cited by 22 publications

(4 citation statements)

References 10 publications

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“…In the current work, the edge of the boundary layer is defined as the location where the total enthalpy is 99 % of the freestream total enthalpy for consistency with Ref. [44,45] who performed a similar analysis.…”

Section: Resultsmentioning

confidence: 99%

“…Hence, it is necessary to resort to thermochemical nonequilibrium Navier-Stokes simulations to answer the abovementioned question. Gökcen [45] presented an investigation of the question by comparing the nonequilibrium stagnation point heat flux computed from two different freestreams with the same total enthalpy but different thermochemical statesone was in equilibrium while the other was frozen at a thermochemical state representative of a nozzle flow in a hypersonic facility. Gökcen showed that for lower total enthalpy conditions around 7 MJ/kg, the nonequilibrium stagnation point heat flux was uninfluenced by the thermochemical state of the freestream provided the total enthalpy was the same.…”

Section: On the Potential Uncertainties Of The Correction Factorsmentioning

confidence: 99%

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Characterization of reflected shock tunnel air conditions using a simple method

Olivier

Wen

et al. 2022

Physics of Fluids

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A new method to characterize air test conditions in hypersonic impulse facilities is introduced. It is a hybrid experimental-computational rebuilding method which uses the Fay-Riddell correlation with corrections based on thermochemical nonequilibrium computational fluid dynamic results. Its benefits include simplicity and time-resolution, and, using this method, a unique characterization can be made for each individual experimental run. Simplicity is achieved by avoiding the use of any optical techniques and overly expensive numerical computations while still maintaining accuracy. Without making any assumptions to relate the reservoir conditions to the nozzle exit conditions, the work done characterizing four test conditions in a reflected shock tunnel is presented. In this type of facility, shock compression is used to produce an appropriate reservoir which is then expanded through a nozzle to produce hypersonic flow. Particular focus is given to the nozzle exit total enthalpy where a comparison is made with the reservoir enthalpy obtained using the measured shock speed and pressure in the shock tube. Good agreement is observed in all cases providing validation of the new approach. Additionally, static pressure measurements showed clearly that conditions III and IV have a thermochemical state which likely froze shortly after the nozzle throat. Also, the nozzle flow is shown to be almost isentropic. Due to the simplicity of the current method, it can be easily implemented in existing facilities to provide an additional independent estimate alongside existing results.

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Section: Resultsmentioning

confidence: 99%

Section: On the Potential Uncertainties Of The Correction Factorsmentioning

confidence: 99%

Characterization of reflected shock tunnel air conditions using a simple method

Olivier

Wen

et al. 2022

Physics of Fluids

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“…The thermodynamic activities a of the components were calculated from their mole fraction χ by where the thermodynamic activity coefficients χ Wat , γ Met , and γ Tol of methanol, water, or toluene in binary mixtures were evaluated either by the simple one-parameter Margules activity model or by the UNIFAC group contribution method …”

Section: Methodsmentioning

confidence: 99%

“…The one-parameter Margules activity model provides a simplified model of the thermodynamic activity of each component of a binary mixture as a function of its mole fraction. Assuming components of similar size, the model describes the difference in the polarity of the components by a parameter A with A = 0 for components with identical polarity and ideal mixing, 0 < A < 2.45 for nonideal but miscible mixtures, and 2.45 < A for partially miscible components.…”

Section: Methodsmentioning

confidence: 99%

Binding of Solvent Molecules to a Protein Surface in Binary Mixtures Follows a Competitive Langmuir Model

Kulschewski

Pleiss

2016

Langmuir

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The binding of solvent molecules to a protein surface was modeled by molecular dynamics simulations of of Candida antarctica (C. antarctica) lipase B in binary mixtures of water, methanol, and toluene. Two models were analyzed: a competitive Langmuir model which assumes identical solvent binding sites with a different affinity toward water (KWat), methanol (KMet), and toluene (KTol) and a competitive Langmuir model with an additional interaction between free water and already bound water (KWatWat). The numbers of protein-bound molecules of both components of a binary mixture were determined for different compositions as a function of their thermodynamic activities in the bulk phase, and the binding constants were simultaneously fitted to the six binding curves (two components of three different mixtures). For both Langmuir models, the values of KWat, KMet, and KTol were highly correlated. The highest binding affinity was found for methanol, which was almost 4-fold higher than the binding affinities of water and toluene (KMet ≫ KWat ≈ KTol). Binding of water was dominated by the water-water interaction (KWatWat). Even for the three protein surface patches of highest water affinity, the binding affinity of methanol was 2-fold higher than water and 8-fold higher than toluene (KMet > KWat > KTol). The Langmuir model provides insights into the protein destabilizing mechanism of methanol which has a high binding affinity toward the protein surface. Thus, destabilizing solvents compete with intraprotein interactions and disrupt the tertiary structure. In contrast, benign solvents such as water or toluene have a low affinity toward the protein surface. Water is a special solvent: only few water molecules bind directly to the protein; most water molecules bind to already bound water molecules thus forming water patches. A quantitative mechanistic model of protein-solvent interactions that includes competition and miscibility of the components contributes a robust basis for solvent and protein engineering.

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Introduction

Wang

2014

Theoretical Modelling of Aeroheating on Sharpened Noses Under Rarefied Gas Effects and Nonequilibrium Real Gas Effects

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Effects of freestream nonequilibrium on convective heat transfer to a blunt body

Cited by 22 publications

References 10 publications

Characterization of reflected shock tunnel air conditions using a simple method

Characterization of reflected shock tunnel air conditions using a simple method

Binding of Solvent Molecules to a Protein Surface in Binary Mixtures Follows a Competitive Langmuir Model

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