The Applicability of Coanda Effect Hysteresis for Designing Unsteady Ventilation Systems

Skotnicka-Siepsiak, Aldona

doi:10.3390/en14010034

“…The obtained results for the values of the critical angles of jet detachment (α D ) and jet reattachment (α A ) (Fig. 4 ) confirm the span of the area of the Coanda effect hysteresis known from the literature 45 , 46 . The value differences between the critical α D detachment and α A attachment angles are about 15°.…”

Section: Resultssupporting

confidence: 85%

Pressure distribution on a flat plate in the context of the phenomenon of the Coanda effect hysteresis

Skotnicka-Siepsiak

¹

2022

Sci Rep

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As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. In the experiment, the Reynolds number ranged from 16,192 to 42,240. A fixed geometry diffuser (Witoszyński nozzle) with a height of 0.60 m, width of 0.02 m and outlet velocity of 11.33–29.57 m/s was used. A plate with a length of 1.00 m and a variable inclination angle was installed at the diffuser outlet. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0° and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90° in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface. The study demonstrated that for a turbulent jet, pressure distribution on a flat plate is determined not only by the plate’s inclination angle, but also by the direction of its rotation.

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“…The obtained results for the values of the critical angles of jet detachment (α D ) and jet reattachment (α A ) (Figure 1) con rm the span of the area of the Coanda effect hysteresis known from the literature [48,49]. The value differences between the critical α D detachment and α A attachment angles are about 15°.…”

Section: Resultssupporting

confidence: 81%

Pressure Distribution On A Flat Plate In The Context of The Phenomenon of The Coanda Effect Hysteresis

Skotnicka-Siepsiak

¹

2021

Preprint

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As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0 degree and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90 degrees in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface.

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“…Geometric changes in structural elements may occur in the elastic and inelastic range. Geometric changes in the inelastic range may be caused by rheological effects, brittle fracture or plasticization, biological and chemical corrosion, physical processes such as cyclic freezing and thawing, excessive moisture caused by leaky roofing or faulty ventilation [48,49], and washing out or dissolving small particles from the material structure. Presented below are examples of historic buildings from the 18th century in which, as a result of defects, changes in the static scheme of structural systems occurred.…”

Section: Defects Resulting In Static Scheme Changes In Structurementioning

confidence: 99%

Research on 18th-Century Building Structures in Terms of Static Scheme Changes

Mackiewicz,

Krentowski,

Zimiński

et al. 2023

Materials

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The evaluation of the technical condition of historic buildings that have operated for several hundred years is a complicated issue. Even buildings that are in very poor condition must be checked and assessed in terms of their further repair, strengthening, or compliance with conditions that allow the facility to be safely operated. Most 18th-century buildings have not survived to this day retaining their original arrangements and structural elements. Renovations and repair work in the past were often carried out using materials of uncertain quality, with repair work of different qualities and without detailed analysis or methodology, based only on the experience of the former builders. In historic structures, the character of the work of individual structural elements has often changed due to significant material degradation, the poor quality of repair work, or the loss of adequate support. When load transfers change, internal forces are redistributed, and, as a result, the static scheme changes. This article presents an overview of identified defects affecting the change in static schemes in historical building structures built in the 18th century, using the example of a historic building with a large number of aforementioned defects. The process of assessing the technical condition of the facility is presented, in which non-destructive testing (NDT) methods were used. Detailed computational analyses were carried out for the wooden roof truss structure, which had partially lost its support.

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The Applicability of Coanda Effect Hysteresis for Designing Unsteady Ventilation Systems

Cited by 8 publications

References 82 publications

Pressure distribution on a flat plate in the context of the phenomenon of the Coanda effect hysteresis

Pressure distribution on a flat plate in the context of the phenomenon of the Coanda effect hysteresis

Pressure Distribution On A Flat Plate In The Context of The Phenomenon of The Coanda Effect Hysteresis

Research on 18th-Century Building Structures in Terms of Static Scheme Changes

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