Application of Full Scale Boundary Layer Measurements to Drag Reduction of Airships

Performance of non-rigid airships operating in the neutral buoyancy condition

“…), or the surface is considered rough, then the work of Nash and Bradshaw (14,15) suggests significant discrepancies in drag may result. Previous wind tunnel experiments designed to determine the effect of small excrescences on the drag of bodies of revolution have given contradictory results (16,17) , but full-scale boundary layer measurements carried-out by Cornish and Boatwater (18) on the Goodyear ZS2G-1 non-rigid airship, support the view that hull cleanliness is important: they found C DS hull reductions of about 30% (compared to the 'ordinary' ZS2G-1 design) could be achieved by removing minor excrescences.…”

“…Cornish and Boatwater (18) measured the hull boundary layer velocity profile at various stations on a hull of a ZS2G-1 in-flight. These measurements were made first when the hull was in its 'ordinary' design state and second when the hull was effectively 'cleaned-up' by smoothing the nose battens and removing other unnecessary excrescences.…”

“…Cornish & Boatwater (18) , ordinary; ▲ Cornish & Boatwater (18) , cleaned-up; Prandtl-Schlichting formula (11) ; ---Goodyear (6) • non-rigid airships listed in Table 1; rigid airships listed in Table 2; Jones et al (36) ,…”

“…, L/d = 6; Cornish & Boatwater (18) , ordinary; ▲ Cornish & Boatwater (18) , cleaned-up; -----Baseline drag relation; ---20% reduction, cleaned-up;…”

Calculation of Viscous Drag and Turbulent Boundary-Layer Separation on Two-Dimensional and Axisymetric Bodies in Incompressible Flows

“…The total drag of the body was obtained by extrapolating the results to the tail end. [35]. Total drag coefficients were obtained by Granville's formula (7.14).…”