function my_special_nav_class( $classes, $item ) {
    if ( is_single() && $item->title == 'Blog' ) {
        $classes[] = 'special-class';
    }
    return $classes;
}
add_filter( 'nav_menu_css_class', 'my_special_nav_class', 10, 2 );

<?php

                 $args = array(
                    'order'                  => 'ASC',
                    'orderby'                => 'menu_order',
                    'post_type'              => 'nav_menu_item',
                    'post_status'            => 'publish',
                    'output'                 => ARRAY_A,
                    'output_key'             => 'menu_order',
                    'nopaging'               => true,
                    'update_post_term_cache' => false );

                 $items = wp_get_nav_menu_items( 'my manu', $args );
                 $page_url = get_permalink();
                 foreach($items as $item ) :
                ?>
                     <li <?php if($item->url == $page_url){?>class="active"<?php }?>><a href="<?php echo $item->url;?>"><?php echo $item->title;?></a></li>
            <?php endforeach;?>
         <!-----------------------------Dynamic manu end---------------------------------------------------->