INTRODUCTION

ESDU 96030⁶ describes the nature of the lateral response to vortex shedding of structures of circular cross section. It then develops a method for calculation of this response together with the data required for its implementation. This method takes account also of the lateral response to buffeting by across-wind atmospheric turbulence components, using the methods of ESDU 89049⁵. Comparisons of predictions with both model and full-scale measurements and a discussion of methods of reducing the response to vortex shedding are also included in ESDU 96030.

The calculation method is complex and it can realistically be implemented only through a computer program. A program is currently available as a Microsoft Excel* spreadsheet Module.

This Item gives guidance on the use of the Excel Module. Section 2 considers installation and running^† of the Module. Section 3 describes the input data required and Section 4 the output produced by the program. Section 5 describes a set of Worked Examples. Appendix A provides some guidance on values for input data.

The method can be applied for the following structure types and flow conditions:

• parallel-sided, tapered and stepped structures,

• circular or regular polygon cross section (8 or more sides),

• smooth or rough surfaces (for structures with ancillaries such as ladders attached, the method applies only if the ancillary is entirely within the main structure wake),

• cantilevered structures and structures between end fixings,

• vertical, horizontal or inclined structures,

• structures with or without strakes,

• uniform or shear flow,

• smooth or turbulent flow,

• normal or yawed flow (a yawed wind affects the response only if the structure is not vertical),

• natural wind (full scale), simulated wind (wind tunnel),

• internal flows in which the structure causes a blockage of less than 10%.

Example applications include stacks (chimneys) and process plant towers, lighting standards and elements of lattice structures.

Several worked examples are described in Section 5 and some guidance on sources of input data is given in Appendix A.

* Microsoft and Excel are trademarks of the Microsoft Corporation

^† Some familiarity with the Microsoft Windows operating system and the Microsoft Excel spreadsheet program is assumed. For further guidance on these topics, consult the appropriate Manuals or Help Files.